A photosensitive metallic surface has a work function `phi` . If a photon of energy `3phi` fall on this surface, the electron is ejected with a maximum velocity of `6xx10^(6)` m/s. When the photon energy is increased to `9phi` , then the maximum velocity of the ejected photoelectrons will be

Options

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

Answer

A

Explanation

`E-phi=1/2 mv^(2)` [Einstein's equation]
`:.(3 phi-phi)/(9phi-phi)=(1/2 mv_(1)^(2))/(1/2 mv_(2)^(2)) " " :.(2phi)/(8phi)=(v_(1)^(2))/(v_(2)^(2))`
`:.(v_(1))/(v_(2))=sqrt(1/4)=1/2`
`:.v_(2)=2v_(1)=2xx6xx10^(6)=12xx10^(6)m//s `