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JEE Advanced 2015Paper 2
Exam
JEE Advanced
Year
2015
Paper
Paper 2
Subject
Physics
Chapter
Dual Nature of Matter

JEE Advanced 2015 · Paper 2 · Physics · Dual Nature of Matter

An electron in an excited state of L i ^ 2 + ion has angular...

An electron in an excited state of Li2+L{i}^{2 +} ion has angular momentum 3h2π\dfrac{3h}{2\pi} . The de Broglie wavelength of the electron in this state is pπα0p\pi{\alpha}_{0} (where a0{a}_{0} is the Bohr radius). The value of pp is

Correct answer

0

Step-by-step solution

From Bohr's law
mvr=nh2π=3h2πmvr = \dfrac{nh}{2\pi} = \dfrac{3h}{2\pi} (from eqes.)
⇒n=3⇒ n = 3
And momentum =mv=3h2\pir= mv = \dfrac{3h}{2\pir}
Now, radius of nth{n}^{th} shell, r=(n2z)a0r = \left(\dfrac{{n}^{2}}{z}\right){a}_{0}
⇒r=(3)23.a0[∵ZLi=3]⇒ r = \dfrac{{\left(3\right)}^{2}}{3} . {a}_{0} \left[∵ {Z}_{Li} = 3\right]
⇒r=3a0⇒ r = 3{a}_{0}
From De Broglie law
wavelength=hMomentumwavelength = \dfrac{h}{Momentum}
⇒λ=hmv=h3h2πr⇒ \lambda = \dfrac{h}{mv} = \dfrac{h}{\dfrac{3h}{2\pi}r}
⇒λ=2\pir3=2π3×3a0⇒ \lambda = \dfrac{2\pir}{3} = \dfrac{2\pi}{3} \times 3{a}_{0}
λ=2πa0=pπa0\lambda = 2\pi{a}_{0} = p\pi{a}_{0}
⇒P=2⇒ P = 2
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