In a Geiger-Marsden experiment, what is the distance of the closest approach to the nucleus of a $7.7$ MeV $\alpha$-particle before it comes momentarily to rest and reverses its direction?
1. $10$ fm
2. $25$ fm
3. $30$ fm
4. $35$ fm

It is found experimentally that $13.6~\text{eV}$ energy is required to separate a hydrogen atom into a proton and an electron. The velocity of the electron in a hydrogen atom is:
1. $3.2\times10^6~\text{m/s}$
2. $2.2\times10^6~\text{m/s}$
3. $3.2\times10^6~\text{m/s}$
4. $1.2\times10^6~\text{m/s}$

According to the classical electromagnetic theory, the initial frequency of the light emitted by the electron revolving around a proton in the hydrogen atom is: (The velocity of the electron moving around a proton in a hydrogen atom is $2.2\times10^{6}$ m/s)

A $10~\text{kg}$ satellite circles earth once every $2~\text{h}$ in an orbit having a radius of $8000~\text{km}$. Assuming that Bohr’s angular momentum postulate applies to satellites just as it does to an electron in the hydrogen atom. The quantum number of the orbit of the satellite is:
1. $2.0\times10^{43}$
2. $4.7\times10^{45}$
3. $3.0\times10^{43}$
4. $5.3\times10^{45}$

The minimum orbital angular momentum of the electron in a hydrogen atom is:
1. $h$
2. $h/2$
3. $h/2\pi$
4. $h/ \lambda$

Let $L_1$ and $L_2$ be the orbital angular momentum of an electron in the first and second excited states of the hydrogen atom, respectively. According to Bohr's model, the ratio $L_1:L_2$ is:
1. $1:2$
2. $2:1$
3. $3:2$
4. $2:3$