Q43 / 60 · JEE Advanced 2015 (Paper 2) · Physics

An electron in an excited state of Li2+ ion has angular momentum 3h2π . The de Broglie wavelength of the electron in this state is pπα0 (where a0 is the Bohr radius). The value of p is

Correct answer: 2

Solution

From Bohr's law
mvr=nh2π=3h2π (from eqes.)
⇒n=3
And momentum =mv=3h2πr
Now, radius of nth shell, r=n2za0
⇒r=323.a0 ∵ZLi=3
⇒r=3a0
From De Broglie law
wavelength=hMomentum
⇒λ=hmv=h3h2πr
⇒λ=2πr3=2π3×3a0
λ=2πa0=pπa0
⇒P=2

Hence, the correct answer is 2.

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