Observation

Part(a).  This was a popular question among the candidates and was treated with ease by virtually all the respondent.  Performance was good.
Part (b):  This question also evokes application of basic principles of physics.  Many candidates were unable to explain the demand of the question.  Many stated that the louder sound heard was due to the table vibrating in resonance with the tuning fork and so they lost marks.  Performance was low.
Part (c): Almost all the candidates scored the full marks in their part.  Performance was good.
Part (d):  Quite a number of the candidates failed to trace the path of a ray through the prism correctly.  This reflected poor grasp of refraction in glass prism.  Omission of arrow(s) on the rays also led to loss of mark.  The formula for calculating refractive index for a triangular glass prism eluded most candidates.  Performance was low.
The expected answers are:
(a) .   Sound wave and radio wave
                  Difference must match to score.
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/       Does not require a material medium for propagation/can

cannot travel through vacuum                   travel through vacuum.

(b)    Vibrating turning fork

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 louder.
 
(c)(i)  Production of stationary wave
-  two waves must be travelling in opposite directions.
-  incident and reflected waves must have the same frequency/wave length.
-  incident and reflected wave must have equal amplitude
-   there must be superposition
-   there must be a barrier.
(ii)   Interference wave patterns
-   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 travelling 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.