Question

if 5% ofthe energy supplied to an incandescent light bulb is radiated as visible light ,how many visible light photons are emitted by 100 walt bulb? assume wavelength of all possible photons to be 5600Å.
​

Answer 1

║⊕ANSWER⊕║

Wavelength = 5600 A

Energy of one photon is E = h\nu = h*c/wavelength

E = 6.63* 10^-34 * 3* 10⁸/(5600* 10⁻¹⁰) = 3.616 * 10⁻¹⁹ J

A 100 watt bulb requires 100 joule of energy per second.

 

Energy radiated by the bulb as visible light per second = 5% of 100

= 5 Joule

 

Number of photons emitted per second

= Energy radiated per sec/ energy of one photon

= 5/(3.616 * 10⁻¹⁹)  

= 1.38 * 10⁻¹⁹

1.38 * 10⁻¹⁹ photons are emitted by 100 watt bulb.