In a photoelectric experiment ultraviolet light of wavelength 280, nm is used with lithium cathode having work function =2.5, eV. If the wavelength of incident light is switched to 400, nm, find out the change in the stopping potential (in V). ( h =6.63 × 10-34, J.,. c =3 × 108, ms -1)

JEE Mains · Physics · STD 12 - Dual nature of radiation and matter

In a photoelectric experiment ultraviolet light of wavelength \(280\, {nm}\) is used with lithium cathode having work function \(\phi=2.5\, {eV}\). If the wavelength of incident light is switched to \(400\, {nm}\), find out the change in the stopping potential (in \({V}\)). \(\left({h}=6.63 \times 10^{-34}\, {J} \cdots\right.\), \(\left.{c}=3 \times 10^{8} \,{ms}^{-1}\right)\)

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Verified Solution

Correct Answer

(A) \(1.3\)

Detailed explanation

\({KE}_{\max }={eV}_{{S}}=\frac{{h} {c}}{\lambda}-\phi\)

\(\Rightarrow {eV}_{{S}}=\frac{1240}{280}-2.5=1.93\, {eV}\)

\(\rightarrow {V}_{{S}_{1}}=1.93\, {V} \ldots\) (i)

\(\rightarrow {eV}_{{S}_{2}}=\frac{1240}{400}-2.5=0.6 \,{eV}\)

\(\Rightarrow {V}_{{S}_{2}}=0.6 \,{V} \ldots\) (ii)

\(\Delta {V}={V}_{{S}_{1}}-{V}_{{S}_{2}}=1.93-0.6=1.33\, {V}\)

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