WAVESThe waves used for TVs are _____ than those used for radios. This is why you might be able to receive radio signals in the shadow of hills, where you wouldn’t get TV signal.

National 4/5 Physics: Waves v3 Created by Miss Gromala 2018

National 4/5

Physics Auchmuty High School

WAVES Class Notes and Questions

National 4/5 Physics: Waves v3 Created by Miss Gromala 2018 2

Contents

Units, Prefixes and Scientific Notation

1. SI units

2. Prefixes and Scientific Notation

3. Scientific Notation Practice

4. Converting Numbers

Wave Properties

5. Transverse and Longitudinal Waves

6. Wave Characteristics

7. Wave Speed

8. Frequency

9. Period

10. The Wave Equation

11. Wave Properties Summary

Diffraction

12. Diffraction

Sound

13. The Speed of Sound

14. Waveforms

15. Noise and Decibels

16. Ultrasound and Solar

Electromagnetic Spectrum

17. Electromagnetic Family

18. Radio waves

19. Microwaves

20. Infrared

21. Visible Light

22. Ultraviolet

23. X-rays

24. Gamma rays

25. EM Spectrum Summary

Refraction

26. Refraction

Problems

Solutions to Problems

Revision Help Sheets

page 5

page 7

page 12

page 13

page 16

page 21

page 22

page 37

page 38


National 5 Data Sheet

Speed of light in materials Speed of sound in materials

Material Speed in m s−1 Material Speed in m s−1

Air 3·0 108 Aluminium 5200

Carbon dioxide 3·0 108 Air 340

Diamond 1·2 108 Bone 4100

Glass 2·0 108 Carbon dioxide 270

Glycerol 2·1 108 Glycerol 1900

Water 2·3 108 Muscle 1600

Steel 5200

Gravitational field strengths Tissue 1500

Gravitational field strength

on the surface in N kg−1

Water 1500

Earth 9·8 Specific heat capacity of materials

Jupiter 23 Material

Specific heat capacity in J kg−1

oC−1 Mars 3·7

Mercury 3·7 Alcohol 2350

Moon 1·6 Aluminium 902

Neptune 11 Copper 386

Saturn 9·0 Glass 500

Sun 270 Ice 2100

Uranus 8·7 Iron 480

Venus 8·9 Lead 128

Oil 2130

Specific latent heat of fusion of materials Water 4180

Material Specific latent heat of fusion in J kg−1

Melting and boiling points of materials

Alcohol 0·99 105

Material

Melting point in oC

Boiling point in oC Aluminium 3·95 105

Carbon dioxide 1·80 105 Alcohol −98 65

Copper 2·05 105 Aluminium 660 2470

Iron 2·67 105 Copper 1077 2567

Lead 0·25 105 Glycerol 18 290

Water 3·34 105 Lead 328 1737

Iron 1537 2737

Specific latent heat of vaporisation of materials

Material Specific latent heat of vaporisation in J kg−1

Radiation weighting factors

Type of radiation Radiation

weighting factor Alcohol 11·2 105

Carbon dioxide 3·77 105 alpha 20

Glycerol 8·30 105 beta 1

Turpentine 2·90 105

fast neutrons 10

Water 22·6 105 gamma 1

slow neutrons 3

X-rays 1


National 5 Relationship Sheet



I can... use appropriate SI units use prefixes: nano (n), micro (μ), milli (m), kilo (k), mega (M), giga (G). use scientific notation

1. SI units

There can be many ways of describing a quantity, for example distance: metres, miles, inches, yards etc. To avoid confusion, scientists have decided on using consistent units internationally. This means that when we are doing calculations involving, for example, a distance, we always use metres.

This system is called the International System of Units — SI units for short.

It is important that we always write down the units that we are using, and convert to the appropriate units when necessary. Here are some SI units we’ll be using:

2. Prefixes and Scientific Notation

Often in physics, we are dealing with very small or very large numbers. In order to save ourselves from writing such numbers as 0.0000000001 or 230 000 000, we use prefixes and scientific notation.

Quantity Unit Unit symbol Symbol

Distance metre m d

Mass kilogram kg m

Time seconds s t

Prefix Symbol Scientific Notation Operation

tera T 1012 x 1 000 000 000 000

giga G 109 x 1 000 000 000

mega M 106 x 1 000 000

kilo k 103 x 1 000

centi c 10-2 ÷ 100

milli m 10-3 ÷ 1 000

micro µ 10-6 ÷ 1 000 000

nano n 10-9 ÷ 1 000 000 000

pico p 10-12 ÷ 1 000 000 000 000

You might notice that centi- (as in centimetres) is the “odd one out”. It doesn’t follow the pattern!

Can you spot the pattern of the others?


3. Scientific Notation Practice

120000 = 1.2 x 105 0.00002 = 2 x 10-5

2300000 = 2.3 x 10

30000000 = 3 x 10

0.005 = 5 x 10

4560000000 = 4.56 x 10

806000 = 8.06 x 10

0.0000000047 = 4.7 x 10

4. Converting Numbers

Kilo or k = x 1000 or x 103 Mega or M = x 1 000 000 or x 106

Centi or c = ÷ 100 or x 10-2 Mili or m = ÷ 1000 or x 10-3

Example 1. Convert 3.2km into metres

3.2km = 3.2 x 1000 = 3200m or 3.2km = 3.2 x 103m

Example 2. Convert 6.2ms into seconds

6.2ms = 6.2 ÷ 1000 = 0.0062s or 6.2ms = 6.2 x 10-3s

Practice Questions

1. Convert into metres

a) 4km =

b) 12.6Mm =

c) 5.7cm =

3. Convert into kilograms (trickier)

a) 4000g =

b) 0.1Mg=

c) 5mg =

minutes to seconds x minutes by 60

hours to seconds x hours by (60 x 60)

days to seconds x days by (24 x 60 x 60)

years to seconds x years by 365 x 24 x 60 x 60

2. Convert into seconds

a) 2.2ms =

b) 720ns =

c) 0.1ms =


Wave Properties

I can...

state that energy can be transferred as waves

state the difference between a transverse and a longitudinal wave and give examples of

these.

state the definitions of frequency, period, wavelength, amplitude and wave speed.

determine the frequency, period, wavelength, amplitude and wave speed for transverse

and longitudinal waves.

do calculations involving d=vt, v=fλ and f=N/t

do calculations involving T=1/f

5. Transverse and Longitudinal Waves

Waves carry __________. The substance the wave travels through is known as the

m_________.

Transverse:

The particles oscillate (vibrate) at _________ angles to the direction of the wave energy.

Examples of transverse waves are ____________ and __________ waves.

Longitudinal:

The particles oscillate back and ___________ in the __________ direction as the motion of the wave (and the energy).

An example of a longitudinal wave is __________.

direction of particles’ motion

direction of wave energy

direction of particles’ motion

direction of wave energy


6. Wave Characteristics

We use the following terms to describe parts of a wave:

Wave Property Definition

Crest Highest point of a wave

Trough Lowest point of a wave

Example 1

Look at this water wave

a) what is its amplitude?

b) what is its wavelength?

a) A = 2m

b) λ = 6 metres ÷ 3 waves = 2m

6m

2m


8. Frequency

Example: What is the frequency if 400 waves are produced in 20s?

N = 400

t = 20s

f = ?

7. Wave Speed The distance travelled by a wave travelling at a constant speed can be calculated using:

Example:

The crest of a water wave moves a distance of 4m in 10 seconds. Calculate the speed of the wave.

The speed of sound in air is 340ms-1 and the speed of light in air is 300 000 000ms-1

(or 3 x 108ms-1). Light travels approximately 1 million times faster than sound!

d = 4m

t = 10s

v = ?

Space for working:


10. The Wave Equation

We can also find the speed of a wave using its frequency and wavelength.

Example

Microwaves have a frequency of 9.4 GHz. Calculate their wavelength.

f = 9.4 GHz = 9.4 x 109 Hz

v = 3 x 108 ms-1

λ = ?

9. Period

We can consider the case for just one wave. The number of waves is 1 and the time taken is

called the _________. The period is measured in ________.

Example

A certain breed of bat emits ultrasound waves with a period of 23µs. Calculate the frequency of the ultrasound.

T = 23µs = 23 x 10-6s

f = ?


11. Wave Properties Summary

Quantity Symbol Unit Unit symbol Definition

Wavelength metre The _____________ between any two repeating points on the wave

Amplitude m The _________ of a wave from the

middle line

Wave speed v The ________ the wave has

travelled per unit time

Frequency f The number of waves passing a point

in __________ second

Period seconds The _______ it takes one wave to

pass a point


Diffraction

I can...

describe what is meant by diffraction

compare short wave and long wave diffraction

use my knowledge of diffraction to explain differences in radio and TV reception

12. Diffraction

All waves will ___________ around obstacles placed in their way. This bending effect is

called ___________. The longer the wavelength the __________ they diffract.

Complete the diagrams:

Short wavelength Long wavelength

A wave with wavelength of 4m will diffract ________ than a wave with wavelength of 2m.

A wave of frequency 1000Hz will diffract ________ than a wave of frequency 50Hz.

The waves used for TVs are _______ than those used for radios. This is why you might be able to receive radio signals in the shadow of hills, where you wouldn’t get TV signal.


Sound

I can...

analyse sound waveforms

describe an experiment to measure the speed of sound in air

describe methods of protecting human hearing

describe some applications of sonar and ultrasound

13. The Speed of Sound

Sound travels as ____________ waves. Sound travels through gases, liquids and ______,

but it will not travel through a __________.

Experiment to measure the speed of sound

Connect two microphones to a __________. Measure the distance between microphones

using a __________.

Make a loud _________. When the sound gets to microphone A the timer __________.

When sound gets to microphone B the timer __________.

Use the __________ between the microphones and the _________ taken by the sound to

get from microphone A to microphone B to calculate the speed of sound using:

The speed of sound in air is ______________.

The speed of light in air is _______________.

Light is much faster than ___________. In a thunderstorm the lightning and thunder are

made at the same _______. We see the ___________ first, because the light waves

travel __________ than the sound, so it gets to us first.


14. Waveforms We can display sound waves on an oscilloscope screen.

The ___________ of a sound wave corresponds to the loudness of the sound. The ___________ of the waves corresponds to the pitch of the sound.

Circle the correct words describing the waveforms:

Amplifiers can be used to make a sound _________. This increases the amplitude.

15. Noise and Decibels

The larger the amplitude the ___________ the sound. Sound level or

loudness is measured in units called ___________ or ____ for short.

Quiet conversation is ____dB. Danger level is ____dB. A loud concert is

_____dB.

Loud sounds can damage your __________, so you should wear ________

protectors, such as _____ plugs, ear muffs or noise ________ headphones.

________ is the name we give to any sounds which we don’t want, such as

traffic.

Enter the following sources into the table:

normal talking, nightclub (1m from speaker),

whispering

Source of sound Sound level (dB)

threshold of pain 140

120

pneumatic drill 100

noise pollution level 90

60

40

background noise at home 20

Quiet / loud High / low frequency





16. Ultrasound and Sonar

Humans can hear sound waves with frequencies between __________ and _________Hz.

Frequencies above 20 000Hz are called ___________, and frequencies below 20 Hz are

called ___________. Put the two names in the correct boxes on the diagram.

When ultrasound travels from one medium into another some of

it ____________ back. We can use this fact for medical

imagining, such as looking at unborn __________. We can also

use ultrasound to break up __________ stones.

Sonar

__________ is used on ships and submarines to detect ______, other vessels, or the

seabed. A pulse of ___________ is sent out from the ship. It __________ off the

seabed or shoal of fish and the echo is detected. We can use the time taken

for the sound to travel back to work out the depth. Bats use the same idea

to work out their surroundings.

Example

Sound travels through water at 1400ms-1. If the ultrasound signal sent from a ship towards

the seabed comes back after 0.5s, what is the depth of the sea?

But that’s the total distance travelled—there and back again.

To get the distance to the seabed we much divide the answer

by 2. So the depth of the sea is:

v = 1400ms-1

t = 0.5s

d = ?

0 10 100 1000 10000 100000

Human 20-20 000Hz

Elephant 5 –12 000Hz

Bat 2000-120 000Hz

Dolphin 75– 150 000Hz

Frequency (Hz)



I can...

state the seven bands of the EM spectrum and put them in order of frequency and

wavelength

give examples of a typical source, detector and application for each of the bands of the

EM spectrum

give examples of hazards associated with each band of the EM spectrum and how to

minimise the risks

state how the energy is linked to frequency

state the speed at which all radiations in the EM spectrum travel

17. Electromagnetic Family

Electromagnetic __________ describes a range, or a family of waves, which all travel at

the same speed: ___ x 10 ms-1. This is known as the speed of _____ and is given the

symbol c. This is a universal speed limit—NOTHING can travel faster than c.

Our eyes are only able to detect one small part of the spectrum (this is the colours that we

see). Here is the full spectrum. Fill in the names of the missing waves.

Radio waves have the longest ___________. Gamma rays have the shortest ___________

and therefore the highest ___________. As the frequency of the wave increases the wave

has more ___________. This means that _________ have the most energy and ________

waves have the least.

In the spectrum the waves which diffract the most are __________ waves, because they

have the ____________ wavelengths.

Radio Visible light

X-rays

R_YG_IV

Increasing _____________

Increasing _____________

Decreasing _____________


18. Radio waves

Radio waves have long ______________, so they are good at _____________ round hills

and buildings. This makes them ideal for carrying radio and ___ programmes to your house.

Radio waves are emitted by _________ circuits and some stars. They can be detected by

using an _________. Radio waves are safe, in fact there are radio waves passing all around

us right now!

19. Microwaves

Microwaves are used to carry signals up to ___________ in space and

between our mobile phones! We can also use them to ______ up food in a

microwave oven. They are emitted by __________ circuits, and can

be detected using an _________, just like radio waves.

Microwaves could cause ________, if concentrated.

20. Infrared

Another name for infrared radiation is ______. It can be detected by a

thermometer. In medicine it can be used in heat treatment of damaged

_________ tissue. Rescue services can use __________ imaging cameras

to find people in dark or smoky places. The signal between your _________ and TV is also

transmitted using infrared waves.

21. Visible Light

This light is made up of a range of different__________. Red has a

__________ wavelength than blue light. A concentrated beam of

visible light of one wavelength is called a _________ beam. It can be

used in laser eye __________.


22. Ultraviolet

Most of our ultraviolet radiation comes from the ______. Too

much of it can _______ the skin, or even worse, cause skin

_________. This is why it’s advised to wear sun _________

when outdoors. Special ____________ chemicals can be printed on

important items, such as money, as __________ markings. These markings

only show up under _____________ light. Ultraviolet light can be used to treat skin

conditions, like ________.

23. X-Rays

X-rays pass through most tissue and cause photographic film to turn _________. However,

X-rays are absorbed by _______ in your body, so the

photographic film behind bones stays white, allowing doctors to

detect, for example, broken bones. Overexposure to X-rays can

cause _______, which is why there is a limit to how many X-rays

you can have in one year. X-rays are created when very _____

electrons hit a metal target.

24. Gamma Rays

Gamma rays are created in the nuclei of _______, during

radioactive decay. Gamma rays can be used to kill

________ cells in your body. Chemicals emitting gamma

radiation can also be injected into your ________ stream.

A gamma camera picks up the _________ radiation being

emitted by the chemicals and creates an image of ______ flow in your body. This is called a

radioactive _________. Overexposure to gamma rays can cause _______. We can detect

gamma rays using a Geiger–Müller tube.


25. EM Spectrum Summary — Fill in the boxes Type

of W

ave

Source

Dete

ctor Approx

imate

W

ave

length

Use

Dange

r of over

exposure

1k

m-1m

1cm

(10-2m

)

10

µm (10

-4m)

Visib

le L

ight

70

0nm

—R

ed

50

0nm

—G

reen

40

0nm

—V

iolet

10

nm (10

-8m)

0

.1 nm (10

-10m)

10

pm (10

-12m)


Example 1

A ray of infrared light has a wavelength of 1400nm. Calculate its frequency.

Example 2

The frequency of a microwave is 2870MHz. Calculate its wavelength.

Example 3

a) How long would it take a beam of infrared radiation to travel 980km?

b) What about ultraviolet over the same distance? Why?

a)

b) 3ms as well, because all electromagnetic radiation travels at the same speed.

Remember

n = nano = x 10-9

M = mega = x 106

speed of light = 3 x 108 ms-1 λ = 1400nm v = 3 x 108ms-1 f = ?

λ = ? v = 3 x 108ms-1 f = 2870MHz

d = 980km v = 3 x 108ms-1 t = ?


Refraction

I can...

state that refraction occurs when waves pass from one medium to another

describe refraction in terms of change in wave speed, wavelength and direction

identify the normal, incident ray, refracted ray, angle of incidence and angle of

refraction on a diagram

26. Refraction

Refraction is the process where the ____________ of a wave changes as it travels from

one medium into a different medium (i.e. air into glass).

If the light travels at an

angle to the normal from

one medium into another

then its _____________

also changes. The frequency of

the light does not change.

Here is a diagram showing a beam

of light travelling from air into the

block then back into air.

Line Q is drawn at _____ to the boundary. It is called the __________. All angles are

measured from the normal to the ray of light.

Complete the path of light in the following diagram showing shite light incident on a glass

prism.

air air glass

3 x 108ms-1 3 x 108ms-1 2 x 108ms-1

normal

angle w = angle of __________________

angle x = angle of __________________

angle y = angle of ____________________

angle z = angle of ____________________

Q

Q w

y

z

x


Answering Problems Guide

Calculations

A standard calculation problem will be worth 3 marks:

1 mark for using the correct equation. 1 mark for correct substitution (putting the numbers in) 1 mark for correct answer with the correct unit.

It is best to write down all your steps to ensure you get as many marks as you can.

Always work in SI units: convert centimetres into metres, hours into seconds before the

calculations, UNLESS the question says otherwise.

Express your final answer with the same number of significant figures as the numbers given in

the question

Written Answers State— “tell me...” give definition, read from a table/diagram etc.

What is meant by — state the meaning of the word or phrase Show that — prove that the number given is correct by performing appropriate calculations to get the same number Describe — give an outline/description of what happens Give one reason — give an explanation, in terms of the physics, for what happens

Explain — Relate cause and effect; make the relationships between things evident; provide why and/or how. May include a diagram. Justify — give reasons, in terms of the physics, that support your answer Label — identify/mark your answer on the diagram Identify — use the information given to pick an answer

Determine — find out using calculations, a scale drawing or a graph Suggest why — explain, in physics terms Predict — Suggest what may happen based on available information. May include calculations. Comment on — this is an explanation usually worth 3 marks. Make at least 3 points in your explanation

Draw — draw a simple, scientific diagram with appropriate labels.

If the question is asking for ONE answer, only give one.

Reread the questions. Then reread your answer to make sure it answers it.

Be specific—NEVER use the word “it”. Specify what you’re talking about. “the car accelerates”

is better than “it accelerates”, “time to go round the track” is better than “the time”.

Don’t use the words “probably”, “possibly”, “about”, “quite”.

Don’t panic



1. Write the following numbers in scientific notation

a. 1001

b. 53

c. 6926300000

d. 0.0000000013

e. 0.13592

f. 0.00361

2. Write the following numbers in decimal notation

a. 1.92 x 103

b. 3.051 x 102

c. 9.35 x 10-6

d. 8.2 x 10-3

e. 0.1 x 10-9

f. 0.1 x 109

3. Calculate

a. 4.13 x 10-15 x 5.4 x 102

b. 1.695 x 104 ÷ 1.395 x 1015

c. 6.97 x 103 x 2.34 x 10-6 + 3.2 x 10-2

4. A boyband released two albums. Their first album sold 5.9 x 105 copies. Their second album sold 1.3 x 106 copies. How many total copies have they sold?


Wave Properties Wave Characteristics

1) What do waves carry?

2) What two types of waves have you studied?

3) Copy and complete the table below to show the wave type of each of the following waves

Water waves, sound waves, light waves, radio waves, microwaves, ultrasound

4) Look at the diagram below and answer the following questions

a) What type of wave is it?

b) The wave is moving from left to right. Describe how the point X on the wave is

moving.

5) A slinky can be used to show different types of waves.

a) What type of wave is the slinky showing here?

b) The wave is moving from left to right. Describe how point X on the wave is moving.

6) Copy and complete the following sentences.

_________________ waves, for example water waves, carry _________ by vibrating at right angles to the direction of the wave’s motion.

_________________ waves, for example sound waves, carry _________ through a

________ where the particles vibrate in the ______ direction as the wave’s motion.

L______________________ T______________________

X

X


Wavelength and Amplitude 1) A-B represents one wavelength in the diagram below. State two other pairs of letters

which represent one wavelength

2) How many waves are shown in each of the diagrams below?

3) The wave train shown below is 20m long. How long is each wave?

4) The wavelength of the waves in the diagram below is 3cm. What is the distance between the start and the end of it?

5) What is the wavelength of the waves in the diagram below?

6) Draw a wave train consisting of 2 waves. Put the labels wavelength and amplitude on your diagram in appropriate places.

7) A stone is thrown into a pond, and a wave pattern is produced as

shown on the right. The wavelength of the waves is 6cm. Calculate the distance, d, travelled by the outside wave.

8) Red light from a laser has a wavelength of 4 x 10-7 m in a

certain glass. How many waves, from this laser, would cover a length of 2 cm in this glass?

A B

C D E F

G

300m

d

a) b)

c) d)


Wave Speed 1) Calculate the average speed for each of the following wave signals, and state whether the signal

is light or sound.

a) 600 000 000 metres covered in 2 seconds

b) 1700 metres covered in 5 seconds

c) 500 metres covered in 1.47 seconds

d) 8600 metres covered in 25.3 seconds

e) 6500 metres covered in 0.000022 seconds

f) 255 metres covered in 0.75 seconds

2) Calculate how far light travels in

3) Calculate how far sound travels in

4) Colin is worried about the dangers of being out on the golf course during a thunder and lightning

storm. He sees a flash of lightning and counts 4 seconds before he hears the clap of thunder. How far away is the storm?

5) A group of physics students set out to measure the speed of sound. The pupils stand a distance of 200 metres from the teacher who has a flash gun and starter pistol. The pupils have to start their stopcock when they see the flash and stop it when they hear the bang. The experiment is

carried out three times and the results are shown in the table below.

a) Calculate the speed of sound from each pupil’s set of measurements

b) From the three results, work out the average value for the speed of sound

6) Spectators are told to stay behind a barrier which is 100m away from where fireworks are being set off at a display. How long will it take spectators to hear a ‘banger’ after they have seen it

explode?

7) During the Edinburgh Tattoo, tourists on Princes Street see the canon smoke from the castle 3 seconds before they hear the bang. How far are they from the castle?

8) A plane spotter sees a military jet and then 4.5 seconds later hears the roar from its engine. How far away is the jet?

Helpful hint: Speed of light in air = 3x108ms-1 Speed of sound in air = 340 ms-1

a) 1 second b) 3 seconds c) 10 seconds

a) 1 second b) 3 seconds c) 10 seconds

Distance from gun to pupils (m) Time recorded (s) speed of sound (m/s)

200 0.63

200 0.62

200 0.65


Frequency

1) Calculate the frequency of each of the following waves:

a) 10 waves passing a point in 5 seconds

b) 240 waves passing a point in 5 seconds

c) 30 waves produced in a time of 60 seconds

d) 9600 waves passing a point in 800 seconds

e) In a 90 second period of time, 4500 waves are produced

f) Every 15 seconds, 300 000 waves are generated

2) If a wave machine produces 5 waves each second what is the frequency of the machine?

3) A man stands on a beach and counts 40 waves hitting the shore in 10 seconds. What is the frequency of these waves?

4) In 100 seconds a particular smoke alarm emits 1 000 000 sound waves. What is the frequency of

the sound waves?

5) A girl is sitting on the edge of a pier. It takes 0·625 seconds for one complete wave to pass underneath her. What is the frequency of the waves?

6) A girl stands on a beach and counts 15 waves crashing onto the shore in a time of 1 minute. What is the frequency of the waves?

7) In a swimming pool a wave machine creates waves with a frequency of 2 Hz. How many waves are produced in 5 minutes?

8) A smoke alarm sends out high-pitched sound waves with a frequency of 12 000 Hz. If the alarm is on for 30 seconds how many waves does it emit?

9) A tuning fork makes a sound with a frequency of 440Hz. How long does it take to produce 2200

waves at this frequency?

10) A clarinet player plays a long note emitting 9000 waves with a frequency of 1500Hz. For how long does she play this note?

11) A woman’s ear detects 4000 sound waves from an alert on her phone. If the frequency of the sound is 8000Hz, how long does the alert last?

12) A pebble was thrown into a still pond and wave ripples were produced at a rate of 3 waves per second. The diagram below represents the wave pattern in the pond a short time after the pebble was dropped. Each line represents one wave.

a) What was the frequency of the waves in Hertz?

b) How many waves are represented in the diagram?

c) How long did it take for this wave pattern to form?


The Wave Equation

1) Calculate the frequency of a radio wave which has a wavelength of 442 m.

2) The navy use long wavelength radio waves for telecommunication.

Calculate the frequency of a radio wave with a wavelength of 8 600 m used by the navy to communicate at sea.

3) If you look in a newspaper or television magazine you will see information on radio and TV programmes. The radio section usually gives you the frequency of each radio station so that you

can find the programme that you want to listen to on the radio. Below is a list of some radio stations you can tune into on medium wave (MW).

a) Virgin Radio MW 1 215 kHz

b) Radio Scotland MW 810 kHz

c) Radio Forth MW 1 548 kHz

Calculate the wavelength of each of these stations in metres.

4) Radio 5 Live broadcasts a news programme called ‘News Extra’ at 7.00 pm on MW 433 m. Calculate the frequency of this broadcast.

5) A television signal is sent in the same way as a radio signal. To broadcast a television programme two radio carrier waves are needed. One wave carries the picture information and one wave

carries the sound information. BBC 1 use a 621·25 MHz radio wave to carry the sound signal and a 615·25 MHz radio wave to carry the picture signal. Calculate the wavelength of each of these carrier waves.

6) How long would it take for a radio signal to travel from the broadcasting station to a radio receiver 40 km away?

7) A long distance lorry driver uses a CB radio to talk to a colleague 48 km away. How long does it take for the radio wave to travel this distance?

Helpful hint:

Radio and television waves are electromagnetic waves, which travel at a speed of 3x108ms-1 through air.


8) Air traffic control sends a radio message to an aeroplane that is preparing to land at Aberdeen airport. The plane is instructed to descend to 1000 m. The plane was 8 km from the control tower when it received the instruction. Calculate how long it took for the radio message to reach

the aeroplane.

9) A pulse of light is transmitted down a fibre optic cable every 0·5 ms. How far does light travel between each pulse?

10) Transatlantic cables are used to carry information over very long distances. If a signal takes 16·7 ms to travel 3 400 km calculate the speed of light in glass under water.

11) When the signals described in Question 10 are received they are very weak. Researchers decide

to use optical amplifiers which will ‘boost’ the signal every 100 km. ‘Boosting’ a signal takes 0·08 ms. How much longer will the information now take to travel the same distance?

12) Blue light of wavelength 410 nm in air and 274 nm in glass is passed down a fibre optic cable of length 6m. What is the frequency of the light:

a) in air?

b) in glass?

13) Laser light of wavelength 850 nm and frequency 2·4x1014 Hz is used to transmit information down a fibre. Calculate:

a) the speed of light in the fibre

b) how long the light takes to travel 600 m down the fibre at this speed.

14) Calculate the frequency of red light (wavelength = 467 nm in glass) as it passes down a piece of fibre optic cable.


Diffraction

1) Waves are able to bend around the edge of an obstacle. What do we call this property of waves?

2) Copy and complete the following diagrams to show the progression of the waves as they pass through the gap.

3) Which of these radio signals will diffract most easily around a hill? Explain your answer.

A — λ = 0.2km B — λ = 100m C — λ = 8000cm

4) Which of these waves will diffract most easily around tall buildings? Explain your answer.

A — f = 50MHz B — f = 500 000 Hz C — f = 800 kHz

5) A hill lies between a radio and television transmitter and a house.

The house is within the range of both the radio and television signals from the transmitter.

In the house, a radio has good reception but a TV has poor reception from the transmitter. Suggest an explanation for this.

6) Drivers in two cars, A and B, are listening to a performance on the radio. The performance is being broadcast on two different wavebands from the same transmitter.

The ratio in car A is tuned to an AM signal of frequency 1152kHz.

The radio in car B is tuned to an FM signal of frequency 102.5MHz.

Both cars drive into a valley surrounded by hills.

The radio in car B loses the signal from the broadcast.

Explain why this signal is lost.


Speed of Sound

1) The following apparatus was set up to measure the speed of sound. Describe how you would use

this to measure the speed of sound.

2) a) During a thunderstorm, what signal is made first—the sound, the light, or are they both made at the same time?

b) Why do we see the light before we hear the sound?

3) The diagram below represents the particle arrangements for an ice cube (solid), changing into water (liquid) and then steam (gas).

By thinking about the arrangement of the particles, do you think sound will travel fastest in a solid, liquid or gas? Explain your answer.

4) During the demolition of some high rise flats in Glasgow spectators saw the explosion first and

heard it 7 seconds later.

a) Why was there a delay?

b) How far away from the explosion were the spectators standing?

Sound Echoes

5) Paul is standing a distance of 100m away from a large building. He shouts loudly and hears and echo.

a) How far away did the sound travel between leaving Peter and returning to him as an echo?

b) If the speed of sound in air is 340ms-1, how long did it take for the sound to return to Paul?

6) Claire is standing 50m away from a large cliff face. She shouts loudly and hears an echo.

a) How far did the sound travel between leaving Claire and returning to her as an echo?

b) If the speed of sound in air is 340ms-1, how long did it take for the sound to return to her?

Sound

ice liquid gas

50m


7) A hiker stands in a canyon and shouts so that she hears an echo from the canyon wall. She records a time of 0.47 seconds between shouting and hearing an echo.

a) How far did the sound travel in this time? (assume v = 340ms-1)

b) Calculate the distance between the hiker and the wall.

8) SONAR (SOund Navigation And Ranging) equipment can be used to find fish under the water.

The sound frequencies used in sonar systems vary from very low to extremely high.

On one particular fishing trip, a sound pulse is transmitted and the echo from the sea bed is

received 0.06 seconds later.

a) How far did the sound pulse travel between transmission and detection? (speed of sound in water 1500ms-1)

b) How deep was the sea at this point?

c) A large fish swam under the boat giving an echo time of 0.02 seconds. Calculate how far

below the boat the fish was swimming.

9) Ultrasound is sound that is so high pitched, humans cannot hear it. During an ultrasound scan a foetus’ forehead is situated 7.5 cm from the transmitter/detector apparatus. The ultrasound pulse, travelling at 1500ms-1 is reflected from the forehead.

a) What is the total distance travelled by the pulse?

b) What time elapses between the transmission of the pulse and the detection of the pulse echo?

10) During an ultrasound scan of a thyroid gland, an ultrasonic pulse, travelling at 1500ms-1 is reflected from a piece of tissue situated 3cm from the transmitter/detector.

a) What is the total distance travelled by the pulse?

b) What time elapses between the transmission of the pulse and the detection of the pulse echo?



1) For each of the 7 bands of the electromagnetic spectrum, state 2 uses.

2) An x-ray photograph is taken of a patient’s knee.

a) At which position should the patient’s knee be placed; X, Y or Z?

b) Why does the nurse stand behind a lead screen while the x-ray machine is operating?

c) Explain how the photographic film shows up the bones in the patient’s knee.

3) a) What is the danger of over-exposure to ultraviolet radiation?

b) Give ways in which this risk can be reduced.

4) Laser pointers use low powered laser beams however these can still be dangerous. What part of

the body would be most easily damaged by this laser light?

5) Over exposure to gamma radiation is dangerous. Explain why.

6) What so all waves in the electromagnetic spectrum have in common?

7) Look at the following diagram of the electromagnetic spectrum.

a) Identify the parts of the spectrum labelled A B C D and E.

b) In which part of the spectrum do the waves have the longest wavelengths?

c) In which part of the spectrum do the waves have the lowest frequencies?

d) In which part of the spectrum do the waves have the highest energy?

e) What colour of visible light has the longer wavelength: red or violet?

X-RAY MACHINE X

Y Z

Photographic film

A B C Visible light

D X-rays E


8) The list below shows frequency bands, wavelength ranges and energies associated with sections of the electromagnetic spectrum.

Spectrum section 3 has the longest wavelength, lowest frequency and lowest energy. It covers Radio waves.

a) Starting with the spectrum section 3, order the sections from lowest to highest frequency

and identify what part of the spectrum each section number relates to.

b) What is the wavelength range of gamma radiation?

c) What is the frequency band of ultraviolet?

d) What range of energies would x-rays have?

e) What section of the electromagnetic spectrum has a wavelength range of

4 x 10-7 to 7 x 10-7 (400—700 nm)?

f) Give suitable wavelength values for red, blue and green light, in nm.

9) An Olympic athlete can run 100m in 10 seconds. How far would a radio wave travel in 10 seconds?

10) On 12 December 1901, Gugliemo Marconi sent the first radio message across the Atlantic ocean. The message travelled a total distance of 3440km between Cornwall in England and Newfoundland in Canada. How long did it take the radio message to travel between England and

Canada?

11) A channel 4 programme is transmitted from an aerial outside Inverness. A radio wave of frequency 645.25 MHz carries the sound signal. The picture signal is carried by a radio wave of frequency 639.25 MHz.

a) Calculate the wavelength of the radio wave carrying the picture signal

b) How long would it take for the sound signal to reach Aberdeen which is 152km from the transmitter.

c) How far would the picture signal travel in 8.5 x 10-4 seconds.

12) A dish aerial at a ground station collects 12GHz signal transmitted by a satellite. The signal took 0.15s to reach the aerial.

a) What is the wavelength of the signal?

b) How far is the satellite from the ground station?

Spectrum section Wavelength range (m) Frequency band (Hz) Energy range of waves (J)

1 4 x 10-7 to 7 x 10-7 4 x 1014 to 7.5 x 1014 3 x 10-19 to 5 x 10-19

2 1 x 10-3 to 1 x 10-1 3 x 109 to 3 x 1011 2 x 10-24 to 2 x 10-22

3 Over 0.1 Less than 3 x 109 Less than 2 x 10-24

4 1 x 10-11 to 1 x 10-8 3 x 1016 to 3 x 1019 2 x 10-17 to 2 x 10-14

5 1 x 10-8 to 4 x 10-7 7.5 x 1014 to 3 x 1016 5 x 10-19 to 2 x 10-17

6 Less than 1 x 10-11 Over 3 x 1019 Over 2 x 10-14

7 7 x 10-7 to 1 x 10-3 3 x 1011 to 4 x 1014 2 x 10-22 to 3 x 10-19

Helpful hint:


13) Microwaves are part of the electromagnetic spectrum and have many uses from telecommunications to cooking. Microwaves of wavelength 12cm are used in ovens to cook food. The human body gives out microwaves too. These microwaves, of wavelength 9cm can, can be

detected by a small aerial placed in contact with the skin. This then allows doctors to measure the temperature of organs inside the body.

Calculate the frequency of microwaves used in ovens.

14) Tony sprained his ankle playing football. The physiotherapist used infrared radiation to heat the tissue in his ankle and help it heal. If the wavelength of the infrared radiation is 1.2 x 10-4m in

air, calculate its frequency.

15) David is suffering from pains in his knees. The doctors in the hospital take a “heat picture”, called a thermogram, of his knees, which shows up inflammation of the joints caused by arthritis. The infrared radiation being given out by the knees has a frequency of 5 x 1012 Hz. Calculate the wavelength of this infrared radiation in air.

16) Our eyes can detect visible light which has wavelengths ranging from 400 nm to 700 nm in air. Light with wavelength of about 400nm is violet in colour. Red light has a wavelength of around 700nm. Calculate the frequencies of violet and red light.

17) The ancient Egyptians used ultraviolet radiation from the Sun’s rays to treat the skin complaint acne. Ultraviolet radiation is still used in hospitals to treat this condition. Calculate the

wavelength of UV radiation that has a frequency of 8.8 x 1016Hz.

18) Gamma rays typically have frequencies above 10 “exahertz” or 1 x 1019Hz. Calculate the wavelength of gamma waves of frequency 1.2 x 1019Hz.

19) Radio waves of frequency 30Hz—3kHz are called extra low frequency (ELF) and are used for communicating with submarines which are moving in deep water.

a) What is the wavelength of a 30Hz ELF wave in air?

b) A navy ship sends a radio message of frequency 3kHz to a submarine directly below it. The signal travels at 2 x 108 ms-1 in water. If the signal takes 3.4 x 10-7 seconds to reach the submarine, calculate the depth, d, at which the submarine is cruising.


Refraction

1) What is meant by the word “refraction”? 2) The diagram below shows light passing through a rectangular block of perspex. a) What name is given to the dotted line?

b) Which angle is the angle of incidence? c) Which angle is the angle of refraction? d) What happens to the speed of the light as the light enters the perspex block? e) What happens to the speed of the light as the light leaves the perspex block?

3) Describe and explain what happens to the wavelength of light as it travels from a less dense medium to a more dense medium.

A B

C D

E

F


Solutions


1. a) 1.001x103 b) 5.3x10

1

c) 6.9263x109 d) 1.3x10

-9

e) 1.3592x10-1

f) 3.61x10-3

2. a) 1920 b) 305.1

c) 0.00000935 d) 0.0082

e) 0.0000000001 f) 100000000

3. a) 2.23x10-12

b) 1.22x10-11

c) 0.05

4. 1.89x106

Wave Characteristics p.22

1. Energy

2. Transverse and Longitudinal

4. a) Transverse b) up and down

5. a) Longitudinal b) left to right

6. transverse, energy, longitudinal, energy, medium, same.

Wavelength and Amplitude p.23

1. CE, FG

2. a) 3 b) 1.5 c) 2 d) 5

3. 5m

4. 15cm

5. 60m

7. 18cm

8. 50000

Wave Speed p.24

1. a)300 000 000m/s, light

b) 340m/s, sound

c) 340m/s, sound

d) 340m/s, sound

e) 300 000 000m/s light

f) 340m/s, sound

2. a) 300 000 000m

b) 900 000 000m

c) 30 000 000 000m

3. a) 340m

b) 1020m

c) 3400m

4. 1360m

5. a) 317, 323, 308 m/s

b) 316 m/s

6. 0.29s

7. 1020m

8. 1530m

Frequency p.25

1. a) 2Hz b) 48Hz

c) 0.5Hz d) 12Hz

e) 50Hz f) 20 000Hz

2. 5Hz

3. 4Hz

4. 10 000Hz

5. 1.6Hz

6. 0.25Hz

7. 600

8. 360000

9. 5s

10. 6s

11. 0.5s

12. a) 3Hz b) 6 waves

c) 2s

The Wave Equation p.26

1. 6.8x105Hz

2. 34 884Hz

3. a) 246.91m b) 370.37m

c) 193.80m

4. 6.93x105Hz

5. picture wave: 0.4m

sound wave: 0.48m

6. 1.33x10-4

s

7. 1.6x10-4

s

8. 2.67x10-5

s

9. 1x105 m

10. 2.04 x 108 m/s

11. 2.72x10-6

s

12. a) 7.3x1014

Hz

b) 7.3x1014

Hz

13. a) 2.04x108 m/s

b) 2.94x10-6

s

14. 4.28x1014

Hz

Diffraction p. 28

1. Diffraction

3. A—longest wavelength diffracts most

4. B—lowest frequency diffracts most

Sound p.29

4. b) 2380m

5. a) 200m b) 0.59s

6. a) 100m b) 0.29s

7. a) 160m b) 80m

8. a) 90m b) 45m

c) 15m

9. a) 0.15m b) 1x10-4

s

10. a) 0.06m

b) 4x10-5

s

Electromagnetic Spectrum p.31

9. 3x109m

10. 0.01s

11. a) 0.47m b) 5.1x10-4

s

c) 255000m

12. a) 0.03m b) 4.5x107m

13. 2.5x109Hz

14. 2.5x1012

Hz

15. 6x10-5

m

16. violet—7.5x1014

Hz

red—4.3x1014

Hz

17. 3.4x10-9

m

18. 2.5x10-11

m

19. a) 1x107m b) 68m

Refraction p.34

2. a) normal b) E

c) B d) decreases e) increases


Revision Help Sheet—National 4

Success criteria

1 Wave Properties

1.1 I can describe the differences between longitudinal and

transverse waves

1.2 I can state the definitions of frequency, wavelength, amplitude

and wave speed

1.3 I can identify wavelength and amplitude of transverse waves

1.4

I can do calculations using

1.5 I can do calculations using d = v t, v = f λ

2 Sound

2.1 I can analyse sound waveforms including changing amplitude and

frequency

2.2 I can describe an experiment to measure the speed of sound in air

2.3 I can state what the decibel scale is measuring

2.4 I can describe methods of protecting human hearing

2.5 I can describe applications of sonar and ultrasound

3 Electromagnetic spectrum

3.1 I can give examples of detectors, applications and hazards for

each of the seven bands of the electromagnetic spectrum

4 Refraction

4.1 I can describe refraction in terms of change of direction where

the angle of incidence if greater than 0 degrees.


Revision Help Sheet—National 5

Success criteria

1 Wave Properties

1.1 I can state that energy can be transferred as waves.

1.2 I can state the definitions of frequency, period, wavelength,

amplitude and wave speed.

1.3 I can state the difference between a transverse and a longitudinal

wave and give examples of these.

1.4 I can determine the frequency, period, wavelength, amplitude and

wave speed for transverse and longitudinal waves.

1.5

I can do calculations involving d = v t, v = f λ , and .

2 Diffraction

2.1 I can describe what is meant by diffraction.

2.2

I can describe the differences between long wave and short wave diffraction and apply these to complete diagrams and explain differences in radio and television reception.

3 Electromagnetic spectrum

3.1 I can state the names of the seven bands of the electromagnetic

spectrum and put them in order of frequency and wavelength.

3.2 I can give an example of a typical source, detector and application

for each of the seven bands of the electromagnetic spectrum.

3.3 I can state how the energy associated with a form of radiation is

linked to its frequency.

3.4 I can state the speed at which all radiations in the

electromagnetic spectrum travel

4 Light

4.1 I can state that refraction occurs when waves pass from one

medium to another

4.2

I can describe refraction in terms of change of wave speed, change in wavelength and change of direction for waves passing into both a more dense and a less dense medium

4.3 I can identify the normal, incident ray, refracted ray, angle of

incidence and angle of refraction on a diagram.

WAVESThe waves used for TVs are _____ than those used for radios. This is why you might be able to receive radio signals in the shadow of hills, where you wouldn’t get TV signal.

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