31. The wavelength of visible region ranges from about ______________:

A.  350 nm to 650 nm                       
B.  400 nm to 700 nm
       
C.  450 nm to 750 nm                       
D.  500 nm to 900 nm
 

32. Objects of temperatures ranges from emit their most intense thermal radiation in the infrared region of spectrum.

A. 50K to 5000K                        
B. 3K to 3000K  
      
C. 250K to 25000K                    
D. 170K to 9000K
 

33. The main technology used in home remote controls is ________________:

A. Microwaves                            
B. X-rays

   
C. Infrared light 
D. Gamma rays 
 

34. Which of following is called oscillator circuit?

A. RC-circuit                       
B. RL-circuit
        
C. LC-circuit                      
D. RLC-circuit

 

35. The current in resistance at resonance in series resonance circuit
is:

A. 2√LC                          
B.  1/√LC
      
C.  1/2√LC                            
D. None of these
 

36. In metal detectors when a metal comes near search coil, its inductance __________ & corresponding oscillator frequency __________.

A. Increases, increases        
B. Increases, decreases
C. Decreases, increases      
D. Decreases, decreases
 

37. Speed of X-rays in vacuum is:

A.  √                        
B.       
C.   1/                             
D. 1/√ 
 

38. A choke is a coil which has:

A.  Thick copper wire             
B.  Large self-inductance    
    
C.  Very small resistance         
D.  All of these
 

39. Which device controls A.C most efficiently?.

A.  Capacitor                       
B.  Resistor      
C.  Inductor                       
D.  All of these
 

40. Out of following which waves have maximum wavelength?

A. X-rays 
B. Infrared rays 
C. γ-rays 
D. Radio waves