If an electron transitions from $n = 5$ to $n = 2$ in a hydrogen spectrum,identify the series and the region of the spectrum.

Given below are two statements.
Statement $I:$ According to Bohr's model of an atom,qualitatively the magnitude of velocity of electron increases with decrease in positive charges on the nucleus as there is no strong hold on the electron by the nucleus.
Statement $II:$ According to Bohr's model of an atom,qualitatively the magnitude of velocity of electron increases with decrease in principal quantum number.
In the light of the above statements,choose the most appropriate answer from the options given below:

In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $3^{rd}$ orbit,what is the total number of spectral lines observed in the infrared region?

Assertion : The radius of the first orbit of hydrogen atom is $0.529 \ \mathring{A}$.
Reason : Radius of each circular orbit $(r_n) = 0.529 \ \mathring{A} \ (n^2/Z)$,where $n = 1, 2, 3$ and $Z =$ atomic number.

The four lowest energy levels of the $H$ atom are shown in the figure. The number of emission lines will be ...... .

When $\alpha$-particles are sent through a thin metal foil,most of them go straight through the foil because (one or more are correct)