Question

A 100 watt light bulb giving monochromatic light of wavelength 6000 Å is placed at the centre of a spherical chamber of radius 0.20 m. It is given that only 50% energy supplied to the bulb is converted into energy. Assuming that the surface of the chamber is perfectly absorbing, the number of photons per second (average) arriving at the surface of spherical chamber is 

(1) 1.51×10²⁰ 

(2) 0.15×10²⁰ 

(3) 15×10²³ 

(4) 15×10¹⁸

Answer 1

Correct option : (1) 1.51×10²⁰ 

Explanation :

Energy of each photon 

Energy of light emitted by the bulb per second E is = 100 x 50/100 = 50 watt

Number of photons reaching the surface per second