Question

A 5 watt LED bulb converts 80% of the power into light photons of wavelength 660nm. What is the number of photons emitted from the bulb in one second ?​

Answer 1

Answer:

Explanation:

We know that,1 Watt=1 J/s, so energy output of 100 W light bulb in one second is 100 J.The actual energy converted to visible light is 20 percent of this value, E=20100×100 E=20 Jλ=662.6 nm=662.6×10−9 mThe energy of one 662.6 nm photon is:E=hcλE=6.626×10−34×3×108662.6×10−9E=0.03×10−17 JThe number of photons needed to produce 20 J of energy is:20×1 photon0.03×10−17=666.67×1017 photons