Question

Find the number of photons emitted per minute by a 25W source of monochromatic light of wavelength 5000Å. Use `h=6.63xx10^(-34)Js`.

Answer 1

Correct Answer - `3.77xx10^(21)`
Here, `P=25W, t=60s`,
`lambda=5000Å=5xx10^(-7)m`,
Energy of a photon,
`E=(hc)/lambda=(6.63xx10^(-34)xx3xx10^(8))/(5xx10^(-7))`
`=3.978xx10^(-19)J`
Energy emitted by source perminute`=E_(1)=Pt`
`E_(1)=25xx60=1500J`.
No. of photons emitted per minute
`N=1500/(3.978xx10^(-19))=3.77xx10^(21)`