KVPY SX SB Exam 2015 Question Paper

Question : 28 of 120

Marks: +1, -0

A beam of monoenergetic electrons, which have been accelerated from rest by a potential U, is used to form an interference pattern in a Young's Double slit experiment. The electrons are now accelerated by potential 4U. The fringe width -

remains the same
is half the original fringe width
is twice the original fringe width
is one-fourth the original fringe width

Validate

Solution:

Debroglie wavelength of electron

λ=h/√{2mK}

Kinetic energy [K = qV]

λ ∝1/√V

Potential becomes four time so wavelength becomes half.
Fringe width

(β)={λD}/d

[β∝λ]

Fringe width becomes half.

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