JEE Main 2022 — Physics Modern Physics

2022integereasy

The stopping potential for photoelectrons emitted from a surface illuminated by light of wavelength $6630Å$ is $0.42V$ . If the threshold frequency is $x\times {10}^{13}s$ , where $x$ is (nearest integer): (Given, speed light $=3\times {10}^{8}m{s}^{-1}$ . Planck's constant $=6.63\times {10}^{-34}Js$ )

Official previous-year question

Held on 26 Jun 2022 · Verified 6 Jul 2026.

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Solution

We know that, $K{E}_{max}=hf-\phi =\frac{hc}{\lambda }-\phi$

Or, $\frac{hc}{\lambda }-\phi =e{V}_{0}$ , where, $\phi =h{\nu }_{\mathrm{th}}$ and ${V}_{0}$ is stopping potential.

So, threshold frequency is

${\nu }_{\mathrm{th}}=\frac{c}{\lambda }-\frac{e{V}_{0}}{h}$

$=\frac{3\times {10}^{8}}{66330\times {10}^{-10}}-\frac{1.6\times {10}^{-19}\times 0.42}{6.63\times {10}^{-34}}$

$=\frac{3}{6.630}\times {10}^{15}-\frac{1.6\times 0.42}{6.63}\times {10}^{15}$

$={10}^{15}(\frac{3}{6.630}-\frac{1.6\times 0.42}{6.63})=0.4524-0.1013$

${\nu }_{\mathrm{th}}=35.11\times {10}^{13}$

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JEE Main 2022 — Physics Modern Physics

2022integereasy

Official previous-year question

Held on 26 Jun 2022 · Verified 6 Jul 2026.

Did you get this right?

Solution

We know that, $K{E}_{max}=hf-\phi =\frac{hc}{\lambda }-\phi$

Or, $\frac{hc}{\lambda }-\phi =e{V}_{0}$ , where, $\phi =h{\nu }_{\mathrm{th}}$ and ${V}_{0}$ is stopping potential.

So, threshold frequency is

${\nu }_{\mathrm{th}}=\frac{c}{\lambda }-\frac{e{V}_{0}}{h}$

$=\frac{3\times {10}^{8}}{66330\times {10}^{-10}}-\frac{1.6\times {10}^{-19}\times 0.42}{6.63\times {10}^{-34}}$

$=\frac{3}{6.630}\times {10}^{15}-\frac{1.6\times 0.42}{6.63}\times {10}^{15}$

$={10}^{15}(\frac{3}{6.630}-\frac{1.6\times 0.42}{6.63})=0.4524-0.1013$

${\nu }_{\mathrm{th}}=35.11\times {10}^{13}$

Your note

JEE Main Modern Physics in other years

Keep practicing Modern Physics

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JEE Main 2022 — Physics Modern Physics

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Solution

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JEE Main Modern Physics in other years

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JEE Main 2022 — Physics Modern Physics

Did you get this right?

Solution

Your note

JEE Main Modern Physics in other years

More JEE Main Modern Physics questions

Other Physics topics for JEE Main

Mechanics

Electromagnetism

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Modern Physics