How many different wavelength may be observed in the spectrum from a hydrogen sample if the atoms excited to states with principal quantum number n?

Explanation

`(n(n-1))/(2)`
`(n(n-1))/(2)=6`
`n^(2)-n-12=0 implies (n-4)(n+3)=0`
n=4
`DeltaE=13.6((1)/(I^(2))-(1)/(4^(2)))=12.75eV`
`lambda=(1242)/(DeltaE(eV))nm`
`=(1242)/(12.75)=97.4 nm`