The electron energy in hydrogen atom is given by `E_(n)=(-2.18xx10^(-18))//n^(2)J`. Calculate the energy required to remove an electron completely from the `n=2` orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

Explanation

`Delta E=E_(oo)-E_(2)=0-(-(2.18xx10^(-18)" J atom"^(-1))/2^(2))=5.45xx10^(-19)" J atom"^(-1)`
`DeltaE=hv=h c/lambda` or `lambda=(hc)/(Delta E)=((6.626xx10^(-34)J s)xx(3xx10^(8) ms^(-1)))/(5.45xx10^(-19) J)=3.647xx10^(-7)m=3.647xx10^(-7)m=3.647xx10^(-5) cm`