In Bohr's model,if the atomic radius of the first orbit is ${r_0}$,then the radius of the fourth orbit is

The angular momentum of the electron in the third Bohr orbit of a hydrogen atom is $l$. What is its angular momentum in the fourth Bohr orbit?

The momentum of an electron revolving in the $n^{\text{th}}$ orbit is given by: (Symbols have their usual meanings)

The radius of the orbit of an electron in a $H$-atom changes from $2.12 \mathring{A}$ to $4.77 \mathring{A}$. The $H$-atom has:

In Bohr's model of the hydrogen atom,which of the following pairs of quantities are quantized?

Assertion : Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate.
Reason : According to classical physics all moving electrons radiate.