Question

A filter transmits only the radiation of wavelength greater than 440 nm. Radiation from a hydrogen-discharge tube goes through such a filter and is incident on a metal of work function 2.0 eV. Find the stopping potential which can stop the photoelectrons.

Answer 1

The stopping potential which can stop the photo electrons is 0.823 volts with wavelength greater than 440 n-m and work function of metal 2.0 eV

Explanation:

Given Data

Radiation’s wavelength coming from filter, λ = 440 n-m

Metal’s work function,  ϕ = 2 eV

Electrons charge, $e = 1.6 \times 10^{-9} C$

Let the stopping potential be denoted as $V_0$.

From the photoelectric equation of Einstein,

$\frac{hc}{\lambda}$ -  ϕ = e$V_0$.  -----------> (1)

where,

h = Constant of Planck  

c = Light’s speed

λ = Radiation wavelength

Substitute the values of h, c, λ and ϕ in equation (1)

$\frac{4.14 \times 10^{-15} \times 3 \times \times 10^{8} }{440 \times 10^{-9} } - 2 = eV_0$

$eV_0= \frac{1242}{440} -2$

e$V_0$ = 2.823 - 2 eV

e$V_0$= 0.823 eV.

$V_0$ = 0.823 Volts

The stopping potential which can sop the photo electrons is 0.823 volts.

Answer 2

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