posted by Vanda .
A special kind of light bulb emits monochromatic light of wavelength 630 nm. Electrical energy supplied to it at the rate of 60W, and the bulb is 93% efficient at converting that energy into light energy. How many photons are emitted by the bulb during its life time of 730h?
find the energy per photon (E=hc/Lambda)
find the total energy: 60*730*3600 watts
solve for number photons
check my thinking.
The correct answer should be numberphotons*hc/lambda=.93*60*730*3600 because the 93% efficiency applies to the bulb and not the energy per photons.