Question

When an electron in hydrogen in hydrogen atom is excited, from its 4th to 5th stationary orbit. The change in angular momentum of electron is: (Planck constant, $ h=6.6\,\times {{10}^{-34}}\,Js $ )

• A. $ 2.09\text{ }Js $
• B. $ 1.05\times {{10}^{-34}}Js $
• C. $ 3.32\times {{10}^{-34}}Js $
• D. $ 4.16\times {{10}^{-34}}Js $

Answer 1

Answer: (B)

Here: Number of initial orbit $ {{n}_{1}}=4 $ Number of final orbit $ {{n}_{2}}=5 $ Now change in angular momentum is given by $ \Delta L={{L}_{2}}-{{L}_{1}}=\frac{{{n}_{2}}h}{2\pi }-\frac{{{n}_{1}}h}{2\pi } $ $ =\frac{h}{2\pi }\left( {{n}_{2}}-{{n}_{1}} \right) $ $ =\frac{6.6\times {{10}^{-34}}}{2\times 3.14}(5-4)=1.05\times {{10}^{-34}}Js $