A photon of wavelenght is ` 4.0 xx 10^(-7) m` strikes on a mnetal surfce , the work function of metal being ` 3. 4xx 10^(-19) J`. Select the correct statyements :

Options

A. The enrgy of pghoton is ` 4. 97 x 10 ^(19) J`
B. The kinetic enrgy fo the emeission is ` 1. 57 xx 10^(-19) J`
C. The kinetic enrgy fo the emission is ` 0.98 eV`
D. The velocity fo photoelectron is ` 5. 87 xx 10^5 ms^(-1)`.

Answer

A, B, C, D

Explanation

`E//"photon" = ( h. c)/(lambda) = ( 6.625 xx 10^(-34) xx 3.0 xx 10^8)/( 4 .0 xx 10^(-7))`
` = 4.97 xx 10^(-19) J`
K.E, of the emission `= E _("photon") - W`
` ( :. W= "work function of metal" )`
` =4. 97 xx 10^(-19) - 3 . 4 xx 10^(-19)`
` = 1. 57 xx 10^(-19) J = 0. 98 eV ( :. 1 eV = 1 . 602 xx 10^(-19) J)`
` :. K.E`. of meitted photoelectron `= 1/2` `mu^2`
` :. u = sqrt (( 2 xx k.E.)/(m))`
` = sqrt(( 2 xx 1. 57 xx 10^(-19))/(9. 1 xx 10^(31))`
` u = 5. 87 xx 10^5 ms^(-1)`.