Social Science
Literature Arabic Islamic Studies C.R.K History MusicVisual Art Clothing/Textile Home Management Shorthand
Physics Paper 2, MAy/June. 2009  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main

General Comments

Question 13

(a) State two differences between a sound wave and a radio wave.

(b) Explain why a vibrating tuning fork sounds louder when its stem is pressed against a table top than when held in air.

(c)State two conditions necessary for the:

  • production of stationary wave in a medium;
  • formation of interference wave patterns;
  • occurrence of total internal reflection of a wave.
(d) A ray of light is incident on one face of an equilateral glass prism.
  • Draw a ray diagram to show the path of the ray through the prism.
  • Calculate the refractive index of the glass if the angle of minimum deviation is 41o.

This question was very popular among the candidates and the overall performance was well above average except in part (c)(ii).

The expected answers were as follows:

(a) Differences between a sound wave and a radiowave

Sound wave Radio wave
is a mechanical wave is an electromagnetic wave
  is longitudinal is transverse
has speed less than speed of light. has speed equal to that of light
requires a material medium for propagation/cannot travel through vacuum.  does not require a material medium for propagation/can travel through vacuum.

(b) The vibrating tuning fork forces the table top to vibrate.  The table top has a much larger area and is therefore in contact with a larger volume of air undergoing vibration.  Hence, sound heard is amplified.
(c)       Conditions necessary for:

            (i)   production of stationary wave
-    Two waves must be traveling in opposite directions.
-     Incident and reflected waves must have the same frequency/wavelength.
-     Incident and reflected waves must have equal amplitude.
-     There must be superimposition.
-     There must be a barrier

(ii)    formation of interference wave pattern
- Two sources must be involved.
- The two sources must be coherent/have a constant phase difference as well as the same frequency and amplitude.
- The waves that are interfering must have the same amplitude
-  The distance between the sources must be of the order of the wavelengths of the waves.

  (iii)   total internal reflection
   -  The wave must be traveling from a denser medium to a less dense medium
   -  The angle of incidence of the wave in the denser medium must be greater than the critical angle for the medium.



(d)(i)  Diagram

                        Correct diagram                                                                                 

            (ii)                  Sin (A + dm)
                      n  = 2                                  
                                   Sin (A/2)
                                  Sin (60 + 41)
                         =                 2
                                  Sin   (60/2)                                                                   

                                        =   1.54  

Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2012 The West African Examinations Council. All rights reserved.