Emission transition in the paschen series end at orbit n=3 and start from orbit n and can be represented as v= 3.29 `xx10^(15) (Hz) (1)/(3^(2) - (1)/(n^(2)))`
Calculate the vallue of n if the transition is observed at 1285 nm . find the region of the spectrum

Explanation

Equation for Paschen series (n=30)
`v= 3.29 xx 10^(15) Hz (1)/(3^(2))- (1)/(n^(2))`
Now value of v put in given equation
2.3346 `xx 10^(14) Hz =3.29 xx 10^(15) ((1)/(3^(2) )-(1)/(n^(2)))`
`(1)/(9) - (1)/(n^(2)) =(2.3346 xx 10^(14) Hz)/( 3.29 xx 10^(15 ) Hz)`
`(1)/(9) -0.071 = (1)/( n^(2))`
`(1)/(n^(2)) = 0.1111- 0.071 =0.040`
so transition occurs n=-5 to n=3 in Paschen series so infrared spectrum