The Bohr orbit radius for the hydrogen atom $(n = 1)$ is approximately $0.530 \ \mathring{A}$. The radius for the first excited state $(n = 2)$ orbit is ........... $\mathring{A}$

Explain Bohr's atomic model.

The energy required to dislodge an electron from an excited isolated $H^-$ ion,given that the ionization energy of a ground state $H$ atom is $IE_1 = 13.6 \ eV$,is:

What is the potential energy of the electron in the $L$ shell of the hydrogen atom? (in $eV$)

The energy required to release $1$ electron from $He^{+}$ is $............$ $eV$.

When a metal surface is irradiated with light of frequency $x \ Hz$,the kinetic energy of emitted photoelectrons is $z \ J$. When the same metal is irradiated with light of frequency $y \ Hz$,the kinetic energy of emitted electrons is $\frac{z}{3} \ J$. What is the threshold frequency (in $Hz$) of the metal?