Question

1. State two factors that determine the speed of electrons emitted from a metal surface by light energy falling on it. 
2. The figure below shows the apparatus used to investigate photoelectric effect of a certain radiation.
   name the labelled parts A, B and C.     
   
3. A photosensitive cathode of work function 2.1ev is irradiated by a radiation of wave length, 4.5 x 10^-7m(Take C = 3.0 x 108ms⁻¹,h = 6.63x10^-34JS and 1ev =1.6 x 10^-19J.)
   Determine:
   The stopping potential on the cathode. (e = 1.6 x 10^-19C)        (3 marks)
4. The graph below shows the stopping potential against frequency of the incident radiation of different colours of light on a photocell.
   
   From the graph determine the threshold wave length. 

Answer 1

1.  
   1. Energy of the incident radiation
   2. Work function of the metal.
2. A-Cathode
   B-Anode
   C-Photocell
3. V_s =  0.6625
           1.6 × 10−19
   V_s= ^hc/_ed −w_o/e
   
4.