Question

4. A modern 200 watt sodium street lamp emits yellow light of wavelength 0.6 um.
Assuming it to be 25% efficiency in converting electrical energy to light, the number of
photons of yellow light it emits per second is


solve with explanation​

Answer 1

Explanation:

The number of photons per sec ,n= amount of  power converted to light /  energy of photon 

Power converted to light Pl=200(25/100)=50W

Energy of photon, Ep=λhc=0.6×10−66.62×10−34×3×108=33.1×10−20J  

Thus, n=33.1×102050=1.5×1020

Hope this help you♥️♥️

Answer 2

Answer:

1.5×1020

6×1018

62×1020

3×1019

Answer :

a

Solution :

Here, P=200W,λ=0.6μm=0.6×10−6,

Energy converted to light =25%

Energy of one photon of yellow light =hcλ

=(6.6×10−34)×(3×108)0.6×10−6=33×10−20J

Energy radiated per second as yellow light

=200×25100=50watt

Number of photons of yellow light emitted per second =5033×10−20=1.7×1020

The closest value is 1.5×1020

Explanation: