Arrange the following wavelengths $(\lambda)$ of given emission lines of $H$ atoms in increasing order:
$(a) \ n = 3 \xrightarrow{\lambda_1} n = 1$
$(b) \ n = 12 \xrightarrow{\lambda_3} n = 10$
$(c) \ n = 5 \xrightarrow{\lambda_2} n = 3$
$(d) \ n = 22 \xrightarrow{\lambda_4} n = 20$
Choose the correct option.

The energy of an electron in the first Bohr orbit of $H$-atom is $-13.6 \ eV$. The possible energy value of an electron in the first excited state of $Li^{2+}$ is (in $eV$)

What is the angular momentum of an electron when it revolves in orbits?

Match List-$I$ with List-$II$.

List-$I$ (Spectral Series for Hydrogen)	List-$II$ (Spectral Region)
$A$. Lyman	$I$. Infrared region
$B$. Balmer	$II$. $UV$ region
$C$. Paschen	$III$. Infrared region
$D$. Pfund	$IV$. Visible region

Choose the correct answer from the options given below:

The following figure shows the spectrum of an ideal black body at four different temperatures. The number of correct statement$(s)$ from the following is $..............$.
$A$. $T_4 > T_3 > T_2 > T_1$
$B$. The black body consists of particles performing simple harmonic motion.
$C$. The peak of the spectrum shifts to shorter wavelength as temperature increases.
$D$. $\frac{T_1}{v_1} = \frac{T_2}{v_2} = \frac{T_3}{v_3} \neq \text{constant}$
$E$. The given spectrum could be explained using quantization of energy.

What is the maximum wavelength in the Lyman series of $He^{+}$ ion?