K.C.S.E Physics Q & A - MODEL 2011PP2QN19

K.C.S.E Physics Q & A - MODEL 2011PP2QN19

​(a) When a radiation was released into a diffusion cloud chamber, short thick tracks were observed. State with a reason, the type of radiation that was detected. 
(b) The half-life of an element X is 3.83 days. A sample of this element is found to have an activity rate of 1.6 x 103 disintegrations per second at a particular time.
Determine its activity rate after 19.15 days. 
(c) State what is meant by an extrinsic semiconductor. 
(d) Figure 12, shows a depletion layer in an unbiased p-n junction.

​State how a battery can be used to make the depletion layer narrower.
(e) Figure 13, shows an incomplete circuit of a full wave rectifier

​(I) Draw in the figure two more diodes to complete the circuit. 
(ii) Show on the figure the points across which the output of the rectifier should obtained. 

answers

​(c) A semiconductor in which impurities have been added to change conductivity.
(d) By connecting it in forward biased mode (i.e. P to + and n to -)