Heat treatment of muscular pain involves radiation of wavelength of about 900nm. Which spectral line of H-atom is suitable for this purpose ? `[R_(H)=1xx10^(5)cm^(-1), h=6.6xx10^(-34)Js, c=3xx10^(8)ms^(-1)]`

Options

A. 1.Paschen , `oo to 3`
B. 2.Lyman , `oo to 1`
C. 3.Paschen , `5 to 3`
D. 4.Balmer , `oo to 2`

Answer

A

Explanation

The wavelength of visible range is 360-720 nm, so wavelength of given radiation is in IR region. So, the line must not belong to Lyman and Balmer series.
`1/lambda=R_H[1/9-1/oo^2]=R_H/9`
`lambda=9/R_H=9/(10^5 cm)=9xx10^(-7)`m =900 nm
So, given spectral line of H-atom is `oo to 3` , Paschen series