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1)

A particle A of mass m and intial velocity v collides with a particle B of mass m2 which is at rest. The collision is head on, and elastic. The ratio of the de-Broglie wavelengths λA to λB after the collision is 


A) λAλB=2

B) λAλB=23

C) λAλB=12

D) λAλB=13

Answer:

Option A

Explanation:

For elastic collision

  Pbefore collision =Pafter collsion

mv=mvA+m2vB

2v=2vA+2vB         .........(i)

Now, coefffficent of restitution,

e=vBvAuAvB

Here uB = 0 ( particle at rest) and for elastic collisione= 1

     1=vBvAvv=vBvA              .............(ii)

From Eq .(i) and Eq .(ii)

                     vA=v3   and vB=4v3

              Hence,  λAλB=(hmVA)hm2VB=VB2VA=4/32/3=2