Question

Number of photons emitted by 10 watt bulb in 10 seconds, if wavelength of the light is 1000 Å, is
a) 1.01 x 1011
b) 2.02 x 1013
c) 3.03 x 1015
d) 4.04 x 1019

Answer 1

Answer:

5.05 x 10^19

Explanation:

Power = Energy/Time

Power = (no.of photonsxenergy of each photon)/s

P = (N/t)(hc/λ)

N = Pλt/hc

= 100(10^-7)/19.8(10^-26)

= (100/19.8)(10^[-7+26])

= 5.05(10^19)

= 5.05 x 10^19

Hence Number of photons emitted = 5.05 x 10^19

All the options are wrong. But you may chose option (d) as the powers are same.