1. Waves Nature

2. What are waves?

3. What are waves?
A wave is a phenomenon in which energy is transferred through vibration.

4. What are mechanical waves?
Mechanical waves are waves which require a medium.
A medium is a form of matter through which the wave travels (such as water, air, glass, etc.)
Waves such as light, x-rays, and other forms of radiation do not require a medium.

5. Type of Waves Transverse Waves
In a transverse wave the matter in the wave moves up and down at a right angle to the direction of the wave. 5

6. Transverse Waves
are waves which travel in a direction perpendicular to the direction of vibrations.
Direction of vibrations
Direction of wave

7. Longitudinal Waves (compression waves)
In a longitudinal wave the matter in the wave moves back and forth parallel to the direction of the wave.

8. sound waves Longitudinal Waves (compression waves)
are waves which travel in a direction parallel to the direction of vibrations.
Direction of vibration
Direction of wave
sound waves
examples include

9. Characteristics of A Wave
Crests and Troughs
Amplitude
Wavelength
Frequency
Period
Speed

10. Crests and Trough Crests are high point of a wave
Troughs are low point of a wave
displacement
crest
distance
trough

11. Check your understood Ans. A , E , I 1. Which points of crests ?
displacement A I E B D F H
distance O J C G
Ans. A , E , I
1. Which points of crests ?
2. Which points of troughs ?
Ans. C , G

12. Amplitude (A) is measured in metres (m)
is the height of a crest or depth of a trough measured from the normal undisturbed positions.
is measured in metres (m)
displacement
distance
crest
trough
Amplitude
Amplitude

13. Wavelength () is measured in metres (m)
is the distance between two successive crests or troughs
displacement
distance
crest
trough
Wavelength
Wavelength
is measured in metres (m)

14. Transverse waves
Longitudinal waves
wavelength 14

15. symbols of wavelength =15

16. Check your knowledge
displacement A I E B D F H
distance O J C G
Which pairs points are called wavelength? (true or false)
A ->C , B -> E , A -> E , D -> F , B -> F

17. f = symbols of frequency = f n = number of wave , t = time frequency
or frequency is the number of waves that pass through a point in one second.
is the number of vibrations in one second
symbols of frequency = f
f =
Unit is waves per second
or Hertz (Hz).
n = number of wave , t = time 17

18. Example > 1 Hz = 1 wave per second.
> 50 Hz is 50 vibrations in 1 second. 18

19. Test Yourselves
Explain the meaning of
35 Hz,
100 Hz ,

20. Wave Period (T) It is the time it takes for one cycle to complete.
It also is the reciprocal of the frequency.
a particle move around
circle. (fig. I)
a period is a time move around circle.
(fig. II) B B A’ A’ A C A A C O D D T

21. SI Unit For Period
is measured in second (s)

22. Relationship between Period (T) and Frequency (f)
f = 100 Hz  T = 1/100 s
f = 40 Hz  T = 1/40 s
f = Hz  T = 1/8 s
f = f Hz  s
frequency is relate period in equation : Hz

24. Speed Of a Wave
is the distance moved in one second.
Wave speed is usually measured in meters/second, but may be measured using other distance units (such as centimeters per second).

25. Recall Speed of a motion = distance  time
where v = speed, s = distance and t = time
wavelength
Distance of wave = =
frequency

26. V = f Wave Equation Speed of a wave = wavelength  period
= wavelength x frequency
V = f
Wave Equation
where v = speed, f = frequency and  = wavelength

27. Example A wave is traveling at a speed of 12 m/s and its
Wavelength is 3 m. Calculate the wave frequency.
Solution
1. This is what you know : speed (v) = 12 m/s , wavelength( ) = 3m.
2. This is you want to find : wave frequency ( f )
3. This is the equation you need to use :
4. Solve for f and then substitute
the known value in the equation.

28. Example Solution This is what to know wavelength ( ) = 2m
The wave in figure are traveling across water. Each wave is 2m long, so that wavelength is 2m. One second later 3 wave have passed the flag. Find wave speed.
Solution
This is what to know
wavelength ( ) = 2m
Frequency (f)= = 3 Hz.
From

29. Problem

30. Question The in A below are traveling across water.
Are the wave transverse or longitudinal?
What is the wavelength of the wave?
What is the amplitude of the wave?
If 2 waves pass the flag every second, what is i) the frequency ii) the period?
Use the wave equation to calculate the speed of wave in A?
What is the wavelength of the wave in diagram B bellow?
If the wave in B have the same speed as those in A, what is their frequency and period?

31. B 1. The diagram shows the outline of a water wave.
What are the values of the amplitude and the wavelength?
amplitude / cm wavelength / cm A B C D B

32. 2. Which wave is longitudinal ?
A light
B radio
C sound
D water C

33. D 3. The speed of 100 Hz wave was measured on four
different days. The results are shown in the table.
On which day the wave have the longest
wavelength ?
day speed of wave
A ms-1
B ms-1
C ms-1
D ms-1 D

34. C 4. A source vibrates at frequency of 20 Hz and
produces waves of wavelength 0.02 m.
At which speed do these waves travel out from
the source ?
A ms-1
B ms-1
C ms-1
D ms-1
Hint:
v = f C

35. 5. A VHF radio station broadcasts at a frequency of. 60MHz (6
5. A VHF radio station broadcasts at a frequency of 60MHz (6.0 x 107 Hz). The speed of radio waves is 3.0 x 108ms-1.
What is the wavelength of the waves broadcast by the station?
A 0.2 m
B 0.5 m
C 2.0 m
D 5.0 m
Hint:
v = f D

36. Nov 1998
6. The diagram shows a coil spring along which a longitudinal wave is moving.
(a) Mark on the diagram a distance equal to the
wave length of the wave [1]
(b) Label on the diagram with the letter C where
the coils of the spring are compressed [1] C C C
Wave length
(continue in next slide)

37. (c) Is the wave on the spring more like a sound wave
(Cont. …) Q 6
(c) Is the wave on the spring more like a sound wave
or a light wave? [1]
Sound wave, because sound wave is a longitudinal
wave but light wave is a transverse wave..

38. 7. The diagram below shows a transverse wave travelling a rope.
wavelength
amplitude
(a) Mark on the diagram which is equal to (i) the wavelength, (ii) the amplitude of the wave. Label your answers [2]
(b) If the wavelength is 0.8m and the frequency is 2 Hz, what is the speed at which the wave moves along the rope ? [2]
v = f = 0.8 x 2 = 1.6 ms-1

39. Nov 1996
8(a) Explain the difference between a transverse and a longitudinal wave [2]
Transverse wave is a wave that its direction of
vibration is perpendicular to the direction of
propagation. It can travel through vacuum.
Longitudinal wave is a wave that its direction of
vibration is parallel to the direction of
propagation. It needs medium to travel.
(b) State one example of each type of wave.
Transverse
Longitudinal [2]
Light
Sound

40. 9.(a) Explain the difference between transverse and
GCE ‘O’ LEVEL Nov 1995
9.(a) Explain the difference between transverse and
longitudinal waves, referring in your answer to
the direction in which the waves travel [2]
Transverse waves are waves that their direction
of vibration is perpendicular to their direction
of propagation.
Longitudinal waves are waves that their
direction of vibration is parallel to their
direction of propagation.
(continue on next slide)

41. (Cont. …) Q. 9
9.(b) The speed of sound in water is 1500m/s. What is a
wave length of a sound wave of frequency 250Hz
travelling through water ? [2]
Since v = f
therefore =  250
 = 1500 / 250 = 6.0 m

42. 10. The diagram shows the air pressure at different
distances from a loudspeaker.
wavelength
amplitude
(a) Mark carefully on the diagram: [2]
(i) a distance which is the wavelength of the
sound wave;
(ii) the amplitude of the sound waves.
(continue on next slide)

43. (Cont. …) Q. 11
11 (b) If the wavelength of a sound wave of frequency
250 Hz is 1.4 m, calculate the speed of the wave.
[2]
since v = f
therefore, = 1.4 x 250
= 350 ms-1

44. 11(a) With the aid of a diagram, explain what is meant
by the frequency and wavelength of a wave. [5]
Frequency is the
number of vibrations
per second.
Wavelength is the distance from a point on a
wave to its next corresponding point.
It usually denote as .. 
(b) What is a longitudinal wave ? [2]
Longitudinal wave is a wave that its direction
of vibration always parallel to the direction of
propagation.
(continue in next slide)