Question

9. A 10 W bulb emits light of 400 nm. The total
number of photons emitted by the bulb in 10 min
is (n = 6.626 x 10-34 Js)
(1) 12 x 1017
(2) 12 1019
(3) 12 x 1021
(4) 12 x 1015​

Answer 1

Answer:

No. of photons=$12\times10^{21}$

So, option (3) is correct

Explanation:

Power and wavelength is given in the queston

Since wavelength is given 400 nm

we can find the energy associated with the wavelength $E=\frac{hc}{wavelength}$

h=planks constant=$6.626\times10^{-34}$, c=speed of light=$3\times10^{8}$

So energy=$4.96\times10^{-19}$ joules.......................(2)

Now we are finding the energy per second=10 $Js$

energy consumed in 10 minutes=6000 $Js$......................(2)

No.of photons=$\frac{energy\  consumed\  in\ 10\ minutes}{energy}$

No.of photons=$\frac{6000}{4.96\times10^{-19} }$

No. of photons=$12\times10^{21}$