Question

A 100 watt bult emits monochromatic light of wavelength 400 nm. Calcualte the number of photons emitted per second by the bulb.

Answer 1

Power of bult`=` 100 watts `= 100 Js^(-1)`
Power `= ("Energy")/("Time")`
Energy of photon `(E ) = hv= ( hc)/(lambda) = ( 6.626 xx 10^(-34)Jsxx3 xx 10^(8)ms^(-1))/( 4 xx 10^(-9) m )= 4.969xx 10^(-33)J`
Number of photons emitted `= ( "Power of the bulb")/("Energy of one photon") = ( 100Js^(-1))/( 4.696xx 10^(-33)J)`
`= 2.012 xx 10^(34)` photons per second