CBSE Class 12 Physics 2015 Delhi Set 1 Paper

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Question : 6
Total: 26
SECTION - B

A proton and an α-particle have the same deBroglie wavelength. Determine the ratio of (i) their accelerating potentials (ii) their speeds.
Solution:  
Ans. Determination of ratio (i) accelerating potential
(ii) speed
(i) λ=
h
2mqV

V=
h2
2mqλ2

mα=4mpqα=2qp
Vp
Vα
=
mαqα
mpqp

=
4mp×2qp
mpqp

=8:1
(ii) λ=
h
mv

v=
h
mλ

vp
vα
=
mα
mp
=4
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