Which of the statements given above is/ are not correct? [CDS 2010]
   (a) 1,2 and 3
   (b) 1 and 2 only
   (c) 2 and 3 only
   (d) 3 only
Ans: (d)
136. The phenomenon of interference can be obtained by :
   (a) two independent sources of light
   (b) two virtual and coherent sources of light
   (c) any two sources whatever be the wavelength or frequency of the light
       waves
   (d) None of these
Ans: (b)
137. The visible range of solar radiation is: [BPSC (Pre) 2011]
   (a) 100- 400 nm
   (b) 400 -700 nm
   (c) 740 - 10000nm
   (d) none of these
Ans: (b)
138. The electrification in a body takes place due to :
   (a) electron
   (b) positron
   (c) proton
   (d) neutron
Ans: (a)
139. The force acting on a particle executing simple harmonic motion is [CDS
   2010]
   (a) directly proportional to the displacement and is directed away from the
       mean position
   (b) inversely proportional to the displacement and is directed towards the
       mean position .
                                        171