Q30. A hydrogen atom changes its state from $n = 3$ to $n = 2$. Due to recoil, the percentage change in the wave length of emitted light is approximately $1 \times 10 ^ { - n }$. The value of $n$ is $\_\_\_\_$ . [Given\\
$\mathrm { Rhc } = 13.6 \mathrm { eV } , \mathrm { hc } = 1242 \mathrm { eVnm } , \mathrm { h } = 6.6 \times 10 ^ { - 34 } \mathrm {~J}$ s mass of the hydrogenatom $= 1.6 \times 10 ^ { - 27 } \mathrm {~kg}$ ]