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Ashok0210
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Asked: 2021-04-27T08:32:14+00:00 In:

Light of frequency 7.21 × 10¹⁴ Hz is incident on a metal surface. Electrons with a maximum speed of 6.0 × 10⁵ m/s are ejected from the surface. What is the threshold frequency for photoemission of electrons?

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Class 12 Physics
CBSE and UP Board
Dual Nature of Radiation and Matter
Chapter-11 Exercise 11.10
NCERT Solutions for Class 12 Physics Chapter 11 Question-10

2020-2021cbse and up boardclass 12 chapter-11 physicsclass 12 physicsdual nature of radiation and matterncert class 12
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      Frequency of the incident photon, v =488 nm = 488 x 10-9 m

      Maximum speed of the electrons, v = 6.0 x 105 m/s

      Planck’s constant, h = 6.626 x 10-34 Js

      Mass of an electron, m = 9.1 x 10-31 kg

      For threshold frequency vo, the relation for kinetic energy is written as:

      1/2 (mv2 )=h(v-v0 )

      v0 = v -mv2 /2h

      = (7.21 x 1014 ) – (9.1 x 10-31) x (6.0 x 105)2 /2 x ( 6.626 x 10-34 )

      = (7.21 x 1014 ) -2.472 x 1014

      = 4.738 x  1014 Hz

      Therefore, the threshold frequency for the photoemission of electrons is 4.738 x 1014 Hz.

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