Question

A certain metallic surface is illuminated with monochromatic . light of wavelength $\lambda$ The stopping potential for photo electric . current for this light is $3v\lambda$ if the same surface is illuminated with light of wavelength 2$\lambda$ the stopping potential is $v_0$ . The threshold wavelength for this surface for photo-electric is

• A. $4\lambda$
• B. $5\lambda$
• C. $6\lambda$
• D. $7\lambda$

Answer 1

The correct option is A $4\lambda$

Ginstein's photoelectric ${equal}^n$

$\frac{h_c}{\lambda }=e\left({3V}_0\right)+W⟶\left(1\right)$

Here, $W=$ work function and $\frac{h_c}{\lambda }=e\left(V_0\right)+W⟶\left(2\right)$

$\frac{h_c}{\lambda }=3\frac{h_c}{2\lambda }-W-3W$

$2W=\frac{h_c}{2\lambda }$

${\lambda }_0=4\lambda$ when ${\lambda }_0=$ threshold wavelength.