When a metal surface is illuminated by light of wavelength λ , the stopping potential is 8 V . When the same surface is illuminated by light of wavelength 3 λ , stopping potential is 2 V . The thresho

Question

When a metal surface is illuminated by light of wavelength λ , the stopping potential is 8 V . When the same surface is illuminated by light of wavelength 3 λ , stopping potential is 2 V . The threshold wavelength for this surface is :

TestHub · Accepted Answer

From photoelectric effect equation, we can write $E = ϕ + K_{m a x}$

and work function can be written as $ϕ = \frac{h c}{λ_{0}}$ .

Also, maximum kinetic energy $K_{m a x} = e V_{0}$

For first case:

$8 e = \frac{h c}{λ} - \frac{h c}{λ_{0}}$ ... (i)

For second case:

$2 e = \frac{h c}{3 λ} - \frac{h c}{λ_{0}}$ ... (ii)

After using equation (ii) in (i), we get

$4 (\frac{h c}{3 λ} - \frac{h c}{λ_{0}}) = \frac{h c}{λ} - \frac{h c}{λ_{0}}$

$\Rightarrow λ_{0} = 9 λ$

Physics - Modern Physics Question with Solution | TestHub

Options:

Doubts & Discussion