Q.
A particle P collides inelastically with a singly ionized helium atom which is at rest. Initially helium atom (He+) is in ground state. After collision particle ‘P’ is found to be scattered at an angle 90° with respect to it’s initial direction of motion, and before emitting any radiation, He+ and particle P have same kinetic energy. The He+ atom after collision was found to be in such an excited state that the maximum possible number of different wavelengths representing the successive transitions in between excited level to ground level is 6. Mark the CORRECT option(s).
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a
The particle P may be a sufficiently energetic electron
b
The particle P may be a sufficiently energetic neutron
c
Out of six wavelengths only one belongs to visible region spectrum
d
No emitted radiations belongs to visible region spectrum
answer is A.
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Detailed Solution
The initial and final situations are marked using Conservation Of Linear Momentum.In x direction, mu+0=0+Mvx⇒vx=muMIn y direction, 0+0+0=mv-Mvy⇒vy=mvMWe are told, KEm=KEM in final state.⇒ 12mv2=12M V2 ⇒ 12mv2=12Mm2M2(u2+v2) (∵from fig, V=vx2+vy2=(muM)2+(mvM)2)⇒ v2=mM(u2+v2) ⇒ v2=mu2M−m , which is possible for M>mHence particle P can be electron or neutronFrom n = 7 to n = 1, 6 maximum possible wavelengths are there, of which n = 4 to n = 3 only belongs to visible spectrum.
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