A bulb emits light of wavelength 4500 Å. The bulb is rated as 150 watt and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second ?

A bulb emits light of wavelength 4500 Å. The bulb is rated as 150 wat

1.	A bulb emits light of wavelength 4500 Å. The bulb is rated as 150 watt and 8% of the energy is emitted as light. How many photons are emitted by the bulb per second ?
Answer» Solution :ELECTRICAL energy in joules = Power in watts `xx` Time in seconds THUS 150 watt = 150 joules of energy emitted per second `:.` Energy emitted as light `= (8)/(100) xx 150 = 12J` `E = n HV = nh (c)/(lamda) " " :. n = (E xx lamda)/(h xx c) = ((12J) xx (4500 xx 10^(-10) m))/((6.626 xx 10^(-34) Js) xx (3 xx 10^(8) ms^(-1))) = 2.717 xx 10^(19)`