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