Waves: Light and Physics Module Form

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. Physics Module Form 5

chapter 1 : Waves

GCKL 2011

1.1

U N D E R S T A N D I N G

W A V E S

What is meant by a wavefront State the direction of propagation of waves in relation to wavefronts What is transverse wave?

An imaginary line that joins all the points on the crest of a wave. The direction of propagation of a wave is perpendicular to its wavefront. A transverse wave is a wave in which particles of the medium oscillate in the direction of the propagation of the waves. Water waves and electromagnetic waves are examples of this type of waves. A longitudinal wave is a wave which the particles of the medium oscillate in the direction parallel to the direction in which the wave moves Sound waves is the example of this type of waves.

What is longitudinal wave?

Fill in the blank with the correct answer given below frequency period Hertz ( Hz) amplitude

1. The amplitude of an oscillation is the maximum displacement for one complete oscillation . 2. The period of the oscillation is the time taken to complete one oscillation.

3. The frequency of the oscillation is the number of complete oscillation made in one second. The SI unit is Hertz ( Hz) Label the graph below and fill in the blank with correct answer. Displacement – time graph

4. In the displacement – time graph as shown above, amplitude is represented by the symbol of a and period is represented by the symbol of T

1-1

. Physics Module Form 5

chapter 1 : Waves

GCKL 2011

Displacement – distance graph

5. In the displacement – distance graph as shown above, amplitude is represented by the symbol of a and wavelength is represented by the symbol of λ 6. Damping is occur when in an oscillating system when the system loses ( gain / loses) energy to surrounding in the form of heat ( heat / chemical ) energy. 7. The force responsible for damping is called dissipative ( equilibrium / dissipative) 8. In a simple pendulum, its natural frequency depending on its mass ). length forces. ( length /

9. When an oscillating systems driven at its natural frequency, the system is said to be at reasonance ( damping / reasonance)

10. A wave travels with a speed of 3.0 x 108 ms-1
(a) What is the frequency of the wave if its wave length is 1.0 m? (b) Another wave is travelling with the same speed but has a frequency of 1.5 x 1012 Hz. What is the wavelength of the wave? Solution. (a) f = 3.0 x 10 1.0 8

Wave speed , v = f λ
(b) λ = v / f = 3.0 x 108 1.5 x 1012 = 2.0 x 10 -4 m

= 3.0 x 108 Hz

1-2

. Physics Module Form 5

chapter 1 : Waves

GCKL 2011

11. The displacement – time graphs and displacement – distance graph describe the motion of a particular wave. Determine the speed of the wave. a) Displacement – time graph (b) Displacement – distance graph S/cm S/c m

t/s 2 4 6 2 4 6 l/cm

solution : v = f λ,

f=1/T from (b) : λ = 4 cm

from (a) : T = 4 s, f = 0.25 Hz
v=fλ

= 0.25 x 4 = 1 cm s-1

12.
Displacement/cm

5
3

-5

1

2
Distance/cm

Based in the displacement-distance graph of a wave, find (a) the amplitude (b) the wavelength of the wave ( ans : 5 cm) ( ans : 2 cm)

13. Calculate the frequency of the given wave below

f = 1/T = 1/4 = 0.25 Hz. 1-3

. Physics Module Form 5

chapter 1 : Waves

GCKL 2011

Practise 1.1 1. 4. The period of oscillations of a simple pendulum increases when the ________________________ increases. A length of the pendulum B mass of the bob of the pendulum C acceleration due to gravity 5. Diagram 1.14 shows a wavefront pattern produces by a dipper vibrating at a frequency of 12 Hz in a ripple tank.

Diagram 1.11 Base on the diagram 1.11 above, which distance represents the amplitude? 2. Diagram 1.12 shows how displacement how varies with time.

Diagram 1.12 Which of the following is true?
Amplitude/ m Period / s Frequency / Hz

Diagram 1.14 What is the speed of the waves? A. 2 cms-1 B. 8 cms-1 -1 C. 12 cms D. 18 cms-1 -1 E. 36 cms

A B C D...
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