A metal is illumimated by light of two different wavelength `248nm` and `310 nm` . The maximum speeds of the photoelectrons corresponding in these wavelength are `u_(1) and u_(2)` respectively . If the ratio `u_(1) : u_(2) = 2 : 1` and `hc = 1240 eVnm `, the work function of the meal is nearly

Options

A. `3:7 eV`
B. `3.2 eV`
C. `2.8 eV`
D. `2.5 eV`

Answer

A

Explanation

`248 nm=1240//248 ev-= 5ev`
`310nm -=1240//310ev=4 ev`
`(K.E_(1))/(K.E_(2))=(4)/(1)=(5ev-W)/(4ev-W)`
`rArr 16-4W=S-W`
`rArr11-3W`
`rArrW=(11)/(3)=3.67 ev ~=3.7 ev`