K.C.S.E Physics Q & A - MODEL 2013PP2QN018

K.C.S.E Physics Q & A - MODEL 2013PP2QN018

​(a) Figure 11 shows plane light waves in air incident on a convex lens whose principal focus is F, the waves move past point G.

​Complete the diagram to show the pattern of the emergent waves between the lens and point G. 
(b)Figure 12 shows crests of circular water waves spreading from two points A and B due to a vibrator. C and D are points on the surface of the water.

​Given that the amplitude of each wave is 5 cm, state with a reason the amplitudes of the waves at point:
(i) C; 
(ii) D. 
(c) Figure 13 shows a standing wave formed when a string of length 1 .5 m stretched between two supports is plucked in the middle.

​(î) Explain how the standing wave is formed. 
(ii) Determine the wavelength of the standing wave. 

answers

(b) (i) 0 cm - trough and crest interference 
(ii) +10 - crest and crest interference 
(c) (i) Waves produced are reflected at the fixed ends. 
Incident and reflected waves interfer constructively at antinodes and destructively at nodes.