The ratio of wavelengths of the last line of the Balmer series and the last line of the Lyman series is:
1. $1$
2. $4$
3. $0.5$
4. $2$

The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom is:
1. $1:1$
2. $1:-1$
3. $2:-1$
4. $1:-2$

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is:

Consider $3^{\text{rd}}$ orbit of $He^{+}$ (Helium). Using a non-relativistic approach, the speed of the electron in this orbit will be: (given $Z=2$ and $h$ (Planck's constant)$= 6.6\times10^{-34}~\text{J-s}$)
1. $2.92\times 10^{6}~\text{m/s}$
2. $1.46\times 10^{6}~\text{m/s}$
3. $0.73\times 10^{6}~\text{m/s}$
4. $3.0\times 10^{8}~\text{m/s}$

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be:
($m$ is the mass of hydrogen atom, $R$ is Rydberg constant and $h$ is Plank’s constant)
1. $\dfrac{24m}{25hR}$
2. $\dfrac{25hR}{24m}$
3. $\dfrac{25m}{24hR}$
4. $\dfrac{24hR}{25m}$