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

8 views

1 Answers

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

8 views