The wavelength of the first spectral line of the Lyman series of the hydrogen spectrum is:
1. $1218$ Å
2. $974.3$ Å
3. $2124$ Å
4. $2120$ Å

In which of the following systems will the wavelength corresponding to $n=2$ to $n=1$ be minimum?

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 transition from the state $n=3$ to $n=1$ in hydrogen-like atoms results in ultraviolet radiation. Infrared radiation will be obtained in the transition from:
1. $3\rightarrow 2$
2. $4\rightarrow 2$
3. $4\rightarrow 3$
4. $2\rightarrow 1$

Which of the following transitions will the wavelength be minimum?
1. $n=5~\text{to}~n=4$
2. $n=4~\text{to}~n=3$
3. $n=3~\text{to}~n=2$
4. $n=2~\text{to}~n=1$