Observation

 

Part (b): This question required the knowledge of refraction as it relates to wavelength, frequency and speed and it was well attempted.
Part (c):  Majority of the candidates were able to copy the diagram.  Amazingly some candidates found it difficult even to copy the given diagram correctly.  Teachers should not relent in taking advantage of always using illustrations in the classroom.  The pattern of the wave after passing through the opening were poorly drawn.
Part (d):  Majority of the candidates were able to write the lens formula but were unable to substitute the date correctly the data because they lacked the knowledge of functionality of the object and image when they are real or virtual.  Generally, performance was average.

The expected answers are:
10.       (a)(i)  Resonance
A phenomenon which occurs whenever a body is set in oscillation at its own natural frequency as a result of impulses received from another body vibrating with the same frequency.  
(ii)    Resonance examples

e.g.   -  repeated jumping of a diver at the free end of a diving board causes the board
to resonate.
-   Xc equals XL in an  L-C-R series circuit for tuning of radio set.
-   rattling of car engine at high speed causing vibration of the body of the car.
-   loud sound from vibrating prongs of a tuning fork.
-   bridge vibrating under uniform matching of soldiers
(Accept any other valid example)

 

               (iii)       Any correct pair   

Intensity	Loudness
The time rate of flow of energy per unit area perpendicular to the direction of propagation of the sound. Depends on physical quantities of energy, time and area.	The magnitude of the sensation resulting from sound reaching the ear. Sensation that depends on the individual hearing  ability.

                                                                         
(b)     Changed wave properties are :
Wavelength                                                                                             

                         Speed                                                                                                                     
                                                                          
(c)
Diagram correctly copied Correct pattern                                                                              
(d)           +   = OR             +   =
+   =-    = 
v  =   - 15 m 

v  =  15 m                   
M  =      = 
= ho     =  6.0m