Unit ( 1 ) grade ( 6 )

Mr / Ismail Etman 1

Think then answer…• How could you hear my voice now?• Very well, with your ears• That is right, but • What make my voice reach your ears to hear it ? • And how did that happen ?• ……………………………………………………………• Also think about, • Why could the light comes from The Sun to The Earth and How ?

10/18/2016

Introduction into Waves

By Teacher / Ismail Etman

Mr / Ismail Etman 3

DO YOU THINK ABOUT THESE WAVES?

In fact, you are right.

But, That is an example for only one type

of waves.10/18/2016

Mr / Ismail Etman 4

FIRST, WHAT ARE WAVES ?

• A Wave :– A disturbance that carries energy

from one place to another.• Waves only transfer energy.• Waves do not transfer matter. How?• Waves need a medium to transfer.

• A Medium :• The material through which the waves travels.

BUT :Some waves do not need a medium to be able to move.

10/18/2016

Mr / Ismail Etman 5

lets discover the types of waves..waves

According to the way to transfer

Transverse waves

Waves in which the medium moves at

normal to the direction of the

wave

Longitudinal waves

Waves in which the medium moves back

and forth in the same direction as

the wave

According to the

medium

Mechanical Wave

a wave needs a medium to be able to move

Electromagnetic WaveA wave can travel without a medium,

(through space)

10/18/2016

Mr / Ismail Etman 6

1. TRANSVERSE WAVES• Waves in which the medium moves at perpendicularly to the direction of the wave. • Parts of transverse waves:

– Crest: the highest point of the wave

– Trough: the lowest point of the wave

10/18/2016

Mr / Ismail Etman 7

2. Compressional (longitudinal) waves:• Waves in which the medium moves back and forth in the same direction as the wave.

• Parts of compressional waves:– Compression: where the particles are

close together– Rarefaction: where the particles are

spread apart

10/18/2016

Mr / Ismail Etman 8

3. Mechanical Wave :• Mechanical Wave a wave needs a medium to be able to move.

– For example : Sound Wave, • It moves through solid faster than water, faster than air. • It may be

– Transverse wave or longitudinal wave.

10/18/2016

Mr / Ismail Etman 9

4. Electromagnetic Wave: • A wave can travel without a medium, (through space).• For example :

– Visible light,– Radio waves,– UV light,– X-rays.

– Note :

• All are Transverse waves

10/18/2016

Mr / Ismail Etman 10

Questions : Multiple Choice• 1. A disturbance that transfers energy from place to place is called a

• Wave.• Medium.• Vibration.• Compression.

• 3. The highest parts of a transverse wave are called• Troughs.• Crests.• Nodes.• Wavelengths.

• 4. Waves that move the particles of the medium parallel to the direction in which the waves are traveling are called

• Longitudinal waves.• Transverse waves.• Surface waves.• Combination waves.

10/18/2016

Lesson 2Propert ies of

wavesBy Teacher / Ismail Etman

Mr / Ismail Etman 12

Wave properties : • Wave properties depend on what (type of energy) makes the wave.

• Descriptive wave properties include:1. Wavelength (λ): - The distance between one point on a wave and the exact same

place on the next wave.- Or, The distance between two consecutive crests or troughs of a transverse

wave.- Or, The distance between two consecutive compressions or rarefactions of

a wave.

>------- Wavelength---< 10/18/2016

Mr / Ismail Etman 13

2. Frequency (f): How many waves go past a point in one second.

The unit of measurement is hertz (Hz). • The higher the frequency, the more

energy in the wave.– If 10 waves go past in 1 second, it is

10 Hz– If 1,000 waves go past in 1 second, it

is 1,000Hz– If 1,000,000 waves go past, it is

1,000,000 Hz

3. The Wave Period (T): The time required for one

cycle. So, the period is the reciprocal of

the frequency.

10/18/2016

Mr / Ismail Etman 14

4. Amplitude (A): – How far the medium (crests and

troughs, or compressions and rarefactions) moves from rest position (the place the medium is when not moving).

• The more energy a wave carries, the larger its amplitude.

5. Wave speed (v): Depends on the medium in

which the wave is traveling. • It varies in solids, liquids and

gases.• A mathematical way to calculate

wave speed is: 1. wave speed = wavelength (m) x

frequency (Hz). Or, v = f x λ.2. wave speed = wavelength (m) / wave

period (s). Or, v = λ / T.

10/18/2016

Mr / Ismail Etman 15

•Problem : • if a wave has a wavelength of 5 m and a frequency of

30 Hz, what is its speed? Answer:

10/18/2016

Mr / Ismail Etman 16

Questions :

•a = …………………….......……………..

•b = ……………………………………....

•c = …………………………....…………..

10/18/2016

•The speed of any wave depends upon A. its energy. B. the medium through which it travels. C. its angle of reflection. D. its amplitude.

• Which of the following statements illustrates the concept that waves carry energy from one place to another:

A. Ocean waves may cause boats to tip over. B. Sunlight heats the surface of the earth. C. Seismic waves cause earthquake damage. D. All of the statements illustrate the concept.

10/18/2016 Mr / Ismail Etman 17