HSC Science (Electronics) 12th Board ExamMaharashtra State Board
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# Find Threshold Frequency and Incident Frequency - HSC Science (Electronics) 12th Board Exam - Physics

ConceptPhotoelectric Effect - Hertz’S Observations

#### Question

The photoelectric work function for a metal surface is 2.3 eV. If the light of wavelength 6800A is incident on the surface of metal, find threshold frequency and incident frequency. Will there be an emission of photoelectrons or not?

[Velocity of light c = 3 x 108 m/s,

Planck’s constant, h = 6.63 * 10-34 Js ]

#### Solution

Given:

phi_0=2.3 eV=2.3*1.6*10^-19 J=3.68*10^-19J

λ=6800 Å=6800*10-10m, c=3*108 m/s, h=6.63*10-34 Js

We know that the incident frequency is given as

v=c/lambda

∴v=(3*10^8)/(6800*10^-10)=4.41*10^14Hz

Now, if the incident frequency is greater than the threshold frequency, then photoelectrons will be emitted from the metal surface. The threshold frequency is given from work function as

v_0=phi_0/h

v_0=(3.68*10^-19)/(6.63*10^-34)=5.55*10^14Hz

Since, photoelectrons v<v_0 will not be emitted.

Is there an error in this question or solution?

#### APPEARS IN

2015-2016 (March) (with solutions)
Question 7.2 | 7.00 marks

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Solution Find Threshold Frequency and Incident Frequency Concept: Photoelectric Effect - Hertz’S Observations.
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