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

Explanation

`v=c/lambda=(3.0xx10^(8) ms^(-1))/(1285xx10^(-9) m)`
`=3.29xx10^(15)(1/3^(2)-1/n^(2))`
or `1/n^(2)=1/9-(3.0xx10^(8))/(1285xx10^(-9))xx1/(3.29xx10^(15))`
`=0.111-0.071=0.04=1/25`
or `n^(2)=25` or `n=5`
The radiation corresponding to `1285 nm` lies in the infrared region.