Question

By what factor the velocity of an electron in a Bohr's orbit for a hydrogen atom will change, if the principal quantum number is doubled:

• A. velocity is doubled
• B. velocity is halved
• C. velocity is reduced to $\frac{1}{3}$
• D. velocity remains unchanged

Answer 1

The correct option is B velocity is halved

In a Bohr's orbit:

Velocity$\propto \frac{Z}{n}$
$\frac{v_1}{v_2}=\frac{n_2}{n_1}$

$\frac{v_1}{v_2}=2$

$v_2=\frac{v_1}{2}$

So, velocity is halved.