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

Explanation

Power of bulb = 100 watt = 100 `JS^(-1)`
Power` =("energy " )/("time")`
energy pf photon (E ) `= hv = (hc )/(lamda )= (6.626 xx10^(-34) Js xx3xx10^(8) ms^(-1))/(400xx10^(-9) m) = 4.969 xx 10 ^(-19)J`
Number of photons emitted `= ( "Power of the bulb ")/( "Energy of one photon ") = ( 100 JS^(-1))/(4.969 xx 10 ^(-19) J) `
` = 2.012 xx 10 ^(20)` photons per second