A bulb emits light of ` 4500 Å `. The bulb is rated as ` 150` watt and ` 9 %` of the energy is emited as light . How many photons are emitted by the bulb per second ?

Explanation

We know ,
Energy one photon `= ( hc)/( lambda) `
` = ( 6. 6625 xx 10 ^(-34) xx 3xx 10^8 )/( 4500 xx 10^(-10)) J = 4 . 42 xx 10^(-19) J`
Energy emitted by bulb`= 15 0 xx 8/( 100 ) J //sec`
Energy emitted by bulb = ` 150xx 8/( 100) J//sec`
`(watt = J//sec )`
`:. n xx 4.44 xx 10 10^(19) = 150 xx 8/( 100) `
( where (n) is no. of photons )
`:. n= 27 . 2 xx 10 ^(18)`.