For a given element the wavelength of the `K_alpha`- line is 0.71 nm and of the `K_beta`- line it is 0.63 nm. Use this information to find wavelength of the `L_alpha` line.

Explanation

`E_(L_alpha) = E_(K_beta) - E_(K_alpha)`
`:. (hc)/(lambda_(L_alpha)) = (hc)/(lambda_(K_beta)) - (hc)/(lambda_(K_alpha))`
or `lambda_(L_alpha) = (lambda_(Kalpha) lambda_(K_beta))`
`=(0.71xx0.63)/(0.71 - 0.63) = 5.59 nm.`