9. Ray optics abd optical instruments — Physics STD 12 Science — Question

$1.$ The quantum number $\mathrm{n}$ of the state finally populated in $\mathrm{He}^{+}$ions is

$(A)$ $2$ $(B)$ $3$ $(C)$ $4$ $(D)$ $5$

$2.$ The wavelength of light emitted in the visible region by $\mathrm{He}^{+}$ions after collisions with $\mathrm{H}$ atoms is

$(A)$ $6.5 \times 10^{-7} \mathrm{~m}$ $(B)$ $5.6 \times 10^{-7} \mathrm{~m}$

$(C)$ $4.8 \times 10^{-7} \mathrm{~m}$ $(D)$ $4.0 \times 10^{-7} \mathrm{~m}$

$3.$ The ratio of the kinetic energy of the $\mathrm{n}=2$ electron for the $\mathrm{H}$ atom to that of $\mathrm{He}^{+}$ion is

$(A)$ $\frac{1}{4}$ $(B)$ $\frac{1}{2}$ $(C)$ $1$ $(D)$ $2$

Give the answer question $1,2$ and $3.$