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. Pashcen, `oorarr3`
B. Lyman, `oorarr1`
C. Paschen, `5rarr3`
D. Balmer, `oorarr2`

Answer

A

Explanation

The wavelength of visible range is `360-720nm`, 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)/(R_(H))-(9)/(10^(5)cm)=9xx10^(-7)=900nm`
So, given spectral line of H-atom is `oorarr3,` Paschen series