Question

If the velocity of hydrogen molecule is $5\times {10}^{4}cmse{c}^{-1}$, then its de-Broglie wavelength is

• A. 2 Å
• B. 4 Å
• C. 8 Å
• D. 100 Å

Answer 1

The correct option is B

4 Å

According to de-Broglie

$\lambda =\frac{h}{mv}=\frac{6.62\times {10}^{-20}erg.sec}{\frac{2}{6.023\times {10}^{23}}\times 5\times {10}^{4}cm/sec}$

$=\frac{6.62\times {10}^{-27}\times 6.023\times {10}^{23}}{2\times 5\times {10}^4}cm=4\times {10}^{-8}cm=4\mathring{A}$.