Question

When green light is incident on a metal , photo electrons are emitted by it but no photo electrons are obtained by yellow light . If red light is incident on that metal then

• A. No electron will be emitted
• B. Less electrons will be emitted
• C. More electrons will be emitted
• D. we can not predict

Answer 1

Answer: (A)

Wavelength of Red $>$ Y ellow $>$ Green
(learn the pattern V IBGY OR)
$\frac{hc}{\lambda }=\frac{hc}{{\lambda }_0}+K.E$
$\therefore$ As we increase $\lambda$, photo electric effect doesn't take place.
If there is no photo electron emission for yellow light, there would be no emission even for red light.