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JEE Main 202125 JulyEvening Shift
Exam
JEE Main
Year
2021
Date
25 July
Shift
Evening Shift
Subject
Physics
Chapter
Dual Nature of Matter

JEE Main 2021 · 25 July · Evening Shift · Physics · Dual Nature of Matter

A light beam of wavelength 500nm is incident on a metal having work...

A light beam of wavelength 500nm500nm is incident on a metal having work function of 1.25eV1 . 25eV, placed in a magnetic field of intensity BB. The electrons emitted perpendicular to the magnetic field BB, with maximum kinetic energy are bent into a circular arc of radius 30cm30cm. The value of BB is ________×10−7T\times {10}^{- 7}T.
Given hc=20×10−26Jmhc = 20 \times {10}^{- 26}Jm, the mass of the electron=9×10−31kg= 9 \times {10}^{- 31}kg.

Correct answer

0

Step-by-step solution

By photoelectric equation

\dfrac{hc}{\lambda} - ϕ = {k}_\max

{k}_\max = \dfrac{1240}{500} - 1 . 25 \approx 1 . 25

r=2mkeBr = \dfrac{\sqrt{2mk}}{eB}

B=2mkerB = \dfrac{\sqrt{2mk}}{er}

=125×10−7T= 125 \times {10}^{- 7}T

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