21. On increasing the frequency of incident light in photoelectric effect:

A. Photoelectric current decrease
       
B. Photoelectric current increases
       
C. Stopping potential increases
       
D. Stopping potential decreases
 

22. If a photon of energy 5.2 eV strikes a metal surface of work function 4 eV, then maximum K.E. of photoelectrons is.:

A. 9.2 eV                                                               
B. 1.5 eV
       
C. 4.2 eV                                                                
D. 1.2 eV
 

23. The slope of the graph between K.Emax of photoelectrons and frequency of incident light gives units of:

A. h                                                                       
B. ℎ/e
C. e/ℎ                                                                        
D. he
 

24. When light of wavelength 100 nm falls on a metal, photoelectrons are \ ejected. If another light of 200 nm is sufficient for photoemission from another metal, then ratio of work function of two metals is:

A. 1:2                                                                         
B. 4:1     
C. 2:1                                                                        
D. 1:4
 

25. A source of light is placed at a distance of 10 cm from photocell and stopping potential is Vo if source is now placed at 20 cm then stopping potential will become:

A. V_o/2                                                                            B. 2V_o    
C. V_o/4                                                                            D. V_o
 

26. During Compton Effect, the wavelength of scattered photon is:

A. Greater than incident photon
B. Lesser than incident photon 
C. Equal to incident photon 
D. Sometimes greater and sometimes smaller then incident  photon.
 

27. Compton shift in wavelength of X-rays photon will be minimum when
scattering angle of photon = .

A. 0o                                                                                  B. 90o    
C. 180o                                                                              D. 45o
 

28. Which one shows wave nature of particles:

A. Photoelectric effect      
B. Compton effect 
C. Pair production
D. Davisson and Germer experiment
 

29. Which of these effects is caused by   ray photons?

A. Photoelectric effect                                       
B. Compton effect  
C. Pair production                                          
D. Annihilation of matter
 

30. The heavy nucleus in pair production conserves:

A. Charge     
B. Energy 
C. Momentum 
D. Energy and momentum