Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • Engineering
  •  When photons of energy strike the surface of a metal <img alt="\mathrm{A}" src="h

 When photons of energy 4.25 \mathrm{eV} strike the surface of a metal \mathrm{A}, the ejected photoelectrons have maximum kinetic energy T_A expressed in \mathrm{eV} and de-Broglie wavelength \lambda_A. The maximum kinetic energy of photoelectron liberated from another metal B by photons of energy 4.70 \mathrm{eV}is \mathrm{T}_B=\left(\mathrm{T}_A-1.50\right) \mathrm{eV}. If the de Broglie wavelength of these photoelectrons is \lambda_{\mathrm{B}}=2 \lambda_{\mathrm{A}}, then choose the wrong option:
 

Option: 1

 the work function of \mathrm{A} \text{ is } 2.25 \mathrm{eV}


Option: 2

the work function of \mathrm{B}\text{ is }4.20 \mathrm{eV}
 


Option: 3

\mathrm{T}_{\mathrm{A}}=2.00 \mathrm{eV}


Option: 4

\mathrm{T}_{\mathrm{B}}=2.75 \mathrm{eV}


Answers (1)

best_answer

We know, \mathrm{K}_{\max }=\mathrm{E}-\mathrm{W}
\begin{aligned} \therefore \quad \mathrm{T}_{\mathrm{A}} & =4.25-\mathrm{W}_{\mathrm{A}} \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad(i)\\ \mathrm{T}_{\mathrm{B}} & =\left(\mathrm{T}_{\mathrm{A}}-1.50\right)=4.70-\mathrm{W}_{\mathrm{B}}\quad \quad \quad \quad(ii) \end{aligned}

From these two equations, we have
\mathrm{W}_{\mathrm{B}}-\mathrm{W}_{\mathrm{A}}=1.95 \mathrm{eV} \quad \quad \quad \quad \quad \quad \quad \quad(iii)

de - Broglie wavelength is given by
\begin{aligned} \lambda & =\frac{\mathrm{h}}{\sqrt{2 \mathrm{Km}}} \quad \text { or } \quad \lambda \propto \frac{1}{\sqrt{\mathrm{K}}} \\ \therefore & \frac{\lambda_{\mathrm{B}}}{\lambda_{\mathrm{A}}}=\sqrt{\frac{\mathrm{K}_{\mathrm{A}}}{\mathrm{K}_{\mathrm{B}}}} \Rightarrow 2=\sqrt{\frac{\mathrm{T}_{\mathrm{A}}}{\mathrm{T}_{\mathrm{A}}-1.5}} \\ \Rightarrow & \mathrm{T}_{\mathrm{A}}=2 \mathrm{eV}, \mathrm{W}_{\mathrm{A}}=2.25 \mathrm{eV}, \mathrm{W}_{\mathrm{B}}=4.20 \mathrm{eV} \text { and } \mathrm{T}_{\mathrm{B}}=0.5 \mathrm{eV} \end{aligned}

Posted by

manish painkra

View full answer

JEE Main high-scoring chapters and topics

Study 40% syllabus and score up to 100% marks in JEE

Similar Questions

Trending Articles/News

anam-khan

JEE Main 2026: JCECEB invites fresh applications for Jharkhand state merit list correction

Latest Question