Question

Find the angular momentum of an electron in the hydrogen atom (initially in ground state) after it absorbs a photon of energy $12.1eV$ .

• A. decreases by $2.11\times 10^{- 34 }Js$
• B. decreases by $1.055\times 10^{- 34 }Js$
• C. increases by $2.11\times 10^{- 34 }Js$
• D. increases by $1.055\times 10^{- 34 }Js$

Answer 1

Answer: (C)

When an electron absorbs energy of $12.1eV$ , it goes to third orbit. And we know that the angular momentum of electron in $n^{th}$ orbit is given by $L=\frac{nh}{2 \pi }$
$\Rightarrow \Delta L=\frac{3 h}{2 \pi }-\frac{h}{2 \pi }$
$\Rightarrow L=\frac{h}{\pi }$ $\Rightarrow L=\frac{6 . 34 \times 10^{- 34}}{\pi }$
$\Rightarrow L=2.11\times 10^{- 34}Js$