The electron energy in hydrogen atom is given by `E_(n) = (-21.7 xx 10^(-12)/(n^(2))) erg`. Calculate the energy required to remove an electron completely from the `n = 2` orbit.What is the longest wavelength (in cm) of light can be used to cause this transition ?

Explanation

` E_2 = (2.18 xx 10^(-18))/2^2 = 5. 45 xx 10^(19) J`
Also ` E_2 = (hc)/(lambda) = ( 2.18 xx 10^(-18))/(2^2)`
` therefore ( lambda) = ( 6.625 xx 10^(34) xx 3.0xx 10^8 xx 2^2)/( 2. 18 xx 10^(-18))`
` = 36 . 46 xx 10^(-8) m= 36.46 xx 10^(-6) cm`
` = 3646 Å`
this will be longest wavelength causing the transiton .