1.

A sodium lamp emits 3.14×1020 photons per second. The distance from the sodium lamp where flux of photon is one photon per second per cm2 :–(a) 5x109 cm (b) 5x108 cm(c) 0.5×109 cm (d) Zero

Answer»

Correct Option (a) 5x109 cm 

Explanation: 

Photon flux at a distance d = no. of photons emitted per second/4πd2

= 3.14 x 1020/4 x 3.14 x d2

d = 5 x 109 cm



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