KVPY SX SB Exam 2016 Question Paper

Question : 30 of 120

Marks: +1, -0

Electrons accelerated from rest by an electrostatic potential are collimated and sent through a Young's double slit setup. The fringe width is w. If the accelerating potential is doubled then the width is now close to -

0.5 w
0.7 w
1.0 w
2.0 w

Validate

Solution:

β={λD}/d

λ=h/{mv}=h/√{2mq\Δv}

β∝λ

∴β∝1/√{\Δv}

as ΔV is double
∴ β is

1/√2

times of

β_\old

∴β_{\new}=0.7β=0.7w

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