Work function of photosensitive surface is `phi` .When photon of `3phi` energy is incident on surface electron with maximum speed of `6xx10^(6)m//s` is emitted from the surface .If energy of photon is changed to `9phi`,maximum speed of photoelectron will be.......

Options

A. `12xx10^(6)m//s`
B. `6xx10^(6)m//s`
C. `3xx10^(6)m//s`
D. `24xx10^(6) m//s`

Answer

A

Explanation

`(1)/(2)mv_(1)^(2)=(hf)_(1)-phi` and `(1)/(2)mv_(2)^(2)=(hf)_(2)-phi`
`=3phi-phi =9phi-phi`
`=2phi=8phi`
`therefore v_(1)^(2)=(v_(2)^(2))/(4)`
`therefore v_(2)=2v_(1)`
`therefore v_(2)=2v_(1)`
`therefore v_(2)=2xx6xx10^(6)`
`therefore v_(2)=12xx10^(6)m//s`