Question

Photons with energy `5 eV` are incident on a cathode `C` in a photoelectric cell . The maximum energy of emitted photoelectrons is `2 eV`. When photons of energy `6 eV` are incident on `C` , no photoelectrons will reach the anode `A` , if the stopping potential of `A` relative to `C` is
A. ` - 1 V`
B. `- 3 V`
C. `+ 3 V`
D. `+ 4 V`

Answer 1

Correct Answer - B
`eV_(s) = (1)/(2) mv_(max)^(2) = hv - phi_(0)`
` 2 = 5 - phi_(0) rArr phi_(0) = 3 eV`
In second case
`eV_(s) = 6 - 3 = 3 eV rArr V_(s) = 3 V`
`:. V_(AC) = - 3 V`