Heat treatment of muscular pain involves radiation of wavelength of about 900 nm. Which spectral line of H atom is suitable for this? Given: Rydberg…

Heat treatment of muscular pain involves radiation of wavelength of about $\displaystyle 900$ nm. Which spectral line of H atom is suitable for this? Given : Rydberg constant $\displaystyle R_H=10^5 \mathrm{~cm}^{-1}, \mathrm{~h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}, \mathrm{c}=3 \times 10^8 \mathrm{~m} / \mathrm{s}$ )