KS4 Waves: KS4 Waves: Character Character
Jan 04, 2016
KS4 Waves: CharacterKS4 Waves: Character
Wave Character: Learning ObjectivesWave Character: Learning Objectives
Understand the nature of wave amplitude, Understand the nature of wave amplitude, wavelength and frequency.wavelength and frequency.
Be able to calculate and convert between Be able to calculate and convert between frequency, period, speed and wavelength.frequency, period, speed and wavelength.
Textbook references:Textbook references: Section 6.01, p.124-125 Section 6.01, p.124-125
Filepath:Filepath: I:\Ph\Y11\11.2 Physics - Mr Peter (PEW)\ I:\Ph\Y11\11.2 Physics - Mr Peter (PEW)\
11.2 Lesson Notes\Waves Topic\11.2 Lesson Notes\Waves Topic\
Lesson 2 - Wave CharacterLesson 2 - Wave Character
Energy and Waves : Review
Waves carry energy from one place to another.
There are 2 main types of wave you need to know about:
Transverse Waves e.g. light waves
Longitudinal Waves e.g. sound waves
Transverse Waves: Review
TRANSVERSE WAVES
A transverse wave can be made using a rope between two people like this :
What type of energy is the wave transferring?
In which direction is the energy moving?
In which direction is each part of the rope moving?
kinetic
Each part of the wave moves at right angles [90º] to the direction the energy is moving in:
Par
ticle
M
ovem
ent
Energy Movement
Transverse Waves : Review
TRANSVERSE WAVES
******
Time
******
a
a = ******
= ******
Dis
plac
emen
t
+
Transverse Waves: Review
TRANSVERSE WAVES
Wavelength and amplitude: reviewWavelength and amplitude: review
What is the wavelength () of a transverse wave?
What is the amplitude (a) of a transverse wave?
It is the ****** between two ****** points on the wave.
It is the ****** of the wave, the bigger the amplitude of the wave, the more ****** it has.
Animation to demonstrate wavelength, Animation to demonstrate wavelength, amplitude and frequencyamplitude and frequency
LONGITUDINAL WAVES
You can make a longitudinal wave using a spring between two people like this :
What type of energy is the wave transferring?
In which direction is the energy moving?
In which direction is each part of the spring moving? [put a marker on the spring to help you see]
******
Longitudinal Waves : Introduction
You should have noticed that each part of the wave moves in the same direction as the direction the energy is moving in:
particle movement
energy movement
When you speak to someone, the air vibrates as a longitudinal wave :
LONGITUDINAL WAVES
Longitudinal Waves : Review
Make a labelled diagram of your spring like this :**
****
Com
pres
sion
****
**
Rar
efac
tion
LONGITUDINAL WAVES
Longitudinal Waves : Review
Frequency: Review
The number of waves passing a point each second is called ****** [ƒ]
Frequency [ƒ] is measured in ****** [Hz]
Frequency [ƒ] = Number of waves passed Time [s]
1 wave per second = 1 Hz
If the wave below passes a point in 1 second, what is it’s frequency?
Frequency and PeriodFrequency and Period The The period period (T) of an oscillation is the (T) of an oscillation is the
time taken for one complete oscillation time taken for one complete oscillation (measured in seconds – s).(measured in seconds – s).
The The frequencyfrequency ( (ff) of an oscillation is the ) of an oscillation is the number of oscillations number of oscillations per secondper second (measured in Hertz – Hz)(measured in Hertz – Hz)
The relationship between the two is:The relationship between the two is:
ff = = 11//TT or or T = T = 11//ff Look at the pendulum on the right. By Look at the pendulum on the right. By
measuring the time taken for measuring the time taken for 5050 swings, swings, can you calculate is period, and hence can you calculate is period, and hence its frequency?its frequency?
6
10
1
3
5
0.5
Calculating Frequency
WaveWave CyclesCycles Time (s)Time (s) Freq (Hz)Freq (Hz)
22
22
22
The Wave Equation
= 2m
1 second later :
Imagine waves on the sea travelling over a shipwreck:
In the diagram, 5 waves pass the shipwreck in 1 second………………….so the frequency = 5 Hz
The wavelength [] = 2 m
This means that the waves travel 10 m in 1 s
……….………………so the speed is 10 m/s
So, in this example, the
frequency X wavelength = speed
5 X 2 = 10
Hz m m/s
This is usually written as :
Waves : wave speed
V = x
For the Extended paper, you will need to be able to change the subject of the formula :
= V and = V
Waves : wave speed
Reminder: Formula trianglesReminder: Formula triangles
v
f
x
Formula triangles help you to rearrange formula. The triangle for the wave equation is shown below:
Whatever quantity you are trying to find cover it up and it will leave you with the calculation required.
So if you were trying to find frequency, f…..
…you would cover f up…
…and you are left with the sum…
f = v
Wave Speed – complete the table
Wave ? [Hz] [m] V [m/s]
Water wave
2 1.5
Mexican wave
40 8
Musical note
256 339
Rope
3 0.8
Ultra-sound
35,000 339
3.0
0.2
1.32
2.4
0.01
Energy and Waves : A Question
The photograph shows waves travelling across the surface of a pond.1m
1) Is this an example of a transverse or longitudinal wave?
2) Estimate the wavelength of the wave:
3) If the frequency of the wave is 0.2 Hz, calculate the speed of the wave:
******
******
******
What are the units of frequency?What are the units of frequency?
A.A. MetresMetres
B.B. Hertz metresHertz metres
C.C. Hertz/metresHertz/metres
D.D. HertzHertz
A wave has a wavelength of 6m and a A wave has a wavelength of 6m and a frequency of 5Hz. frequency of 5Hz. What is the speed of the wave? What is the speed of the wave?
A.A. 1.2 m/s1.2 m/s
B.B. 0.88 m/s0.88 m/s
C.C. 3.0 m/s3.0 m/s
D.D. 30 m/s30 m/s
Wave Character QuestionsWave Character Questions1.1. Name Name twotwo similarities and similarities and oneone difference between difference between
transverse and longitudinal waves.transverse and longitudinal waves.
Answer:Answer:
2.2. Draw a transverse wave and label the amplitude (A), Draw a transverse wave and label the amplitude (A), wavelength (wavelength (), crest (C), and trough (T).
Wave Character QuestionsWave Character Questions3. The surface of a drum vibrates 300 times in one minute.
What is the frequency of the sound wave produced, and how many waves travel out from the drum in 5 seconds?Answer:
4. For the drum in question (3) above, if the speed of sound in air is 330 m/s, what is the wavelength of the sound?Answer:
Wave Character QuestionsWave Character Questions5. Using your textbook and/or the Internet, give three
examples each of transverse and longitudinal waves in nature.Answer:
Wave Character: Learning ObjectivesWave Character: Learning Objectives
Understand the nature of wave Understand the nature of wave amplitude, wavelength and frequency.amplitude, wavelength and frequency.
Be able to calculate and convert between Be able to calculate and convert between frequency, period, speed and frequency, period, speed and wavelength.wavelength.
Textbook references:Textbook references: Section 6.01, p.124-125 Section 6.01, p.124-125
Homework: Textbook page 144, Question 1Homework: Textbook page 144, Question 1