Waves I Questions and Answers - Physics Form 2 Topical Revision

Questions

1. The figure below shows the displacement – time graph for a certain wave
   
   Determine the frequency of the wave?
2. State one effect that would be observed when water waves pass from deep to shallow water.
3. A source generates 40 waves in a second. If the wavelength is 8.5 cm. Calculate the time taken to reach a wall 102m from the source.
4. Name a property of light that shows it is a transverse wave.
5. State ONE difference between mechanical and electromagnet waves.
6. Explain the following terms and state their S.I units
   1. Wavelength
   2. Amplitude
   3. Periodic time
   4. Frequency
7. State THREE differences between light waves and sound waves.
8.  
   1. Name two types of progressive wave motion
   2. Distinguish between the waves stated in 3 (a) above
9.  
   1. The figure below shows a displacement – time graph of a wave. The velocity of the wave is 50cm/s.
      
      Determine the 
      1. Amplitude
      2. Period
      3. Wavelength
      4. Frequency
   2. State ONE factor that does not change as water moves from shallow to deep part.
10. Give an example which show that speed of a wave depends on the medium in which it travels.
11. Give an example to demonstrate that waves carry energy
12. Best FM station broadcasts on a frequency of 250 KHz and the wavelength of its signals is 1200m.
    1. Calculate the speed of radio waves in m/s
    2. The wavelength of the signal of another station that broadcasts on a frequency of 200KHZ.

Answers

1. 1½ → 3.5 x 10^-3
   1 → T
   ∴ T= 1 ÷ ³/₂ x 3.5 x 10^-3
   = 1 x ²/₃ x 3.5 x 10^-3
   =⁷/₃ × 10^-3 Sec
   But f = ¹/_T
   1÷ ⁷/₃ x 10^-3
   = 1 x     3     
            7x10-3 
   = 3 x 10³
         7
   =429 Hz
2. Speed and wavelength decreases
3. f= 40Hz λ=8.5m
   V= fλ
   = 40 x 8.5
   = 340m/s
   T= ^d/_s = ¹⁰²/₃₄₀
   = 0.3sec
4. It can be polarized
5. Mechanical waves requires a material medium to travel through. Electromagnetic waves don’t.
6.  
   1. Wavelength- This is the distance between two successive crests or troughs. SI Unit is Metre (m)
   2. Amplitude – It is the maximum displacement of particles of a medium from the mean/fixed position in either direction. SI Unit is metre (m)
   3. Periodic time – It is the time taken to complete one oscillation. SI Unit is second(s)
   4. Frequency – Is the number of complete oscillations made by a particle in unit time. SI unit is Hertz (Hz)
7.  
   

   Light waves	Sound waves
   Transverse	Longitudinal in nature
   Require no material; medium	Need a medium
   Have short wavelength	Have very long wavelength

8.  
   1.  
      1. Transverse wave
      2. Longitudinal wave
   2. Transverse wave is one in which the movement of each particle is at right angle to the direction of travel of the wave. While longitudinal is where the movement of each particle is parallel to the direction of travel of the wave motion.
9.  
   1.  
      1. Amplitude = 0.6cm
      2. Period = 2 seconds
      3. Wavelength
         λ=Vt
         = 50 x 2
         =100cm
      4. Frequency
         F=¹/_T
         = ½ 
         = 0.5HZ
   2. Frequency
10. In refraction of water waves, the wave speed is reduced in shallower region in a ripple tank.
11. Water waves hitting the beaches have energy which causes weathering.
12.  
    1. The speed of radio wave in m/s 
       Solution
       V= fλ
       = (1200 x 250 x 1000)ms^-1
       = 3.0 x 108 m/s
    2. Wavelength = ^v/_f
       3.0 x 10⁸
       2.0x10⁵
       = 1.5 x 10³
       =1500m