A `12.5eV` electron beam is used to bombard gaseous hydrogen at room temperature. What serious of wavelength will be emitted?

Explanation

Energy of electron beam, E=12.5 eV
Planck's constant `h=6.62xx10^(-34)J`
So, using the relation , `E=(hc)/(lambda),` we get
`lambda(hc)/(E)=(6.62xx10^(-34)xx3xx10^(8))/(12.5xx1.6xx10^(-19))`
`=0.993xx10^(-7)m`
`=993xx10^(-10)m=933Å`
This wavelenght falls in the range of Lyman series `(912Å "to" 1216Å)`, thus we conclude that Lyman series is emitted.