Correct Answer - D
KEY CONCEPT :
`lambda_(min) = (he)/(E )`
`:.lambda_(min) = (12400)/(80 xx 10^(3)) Å = 0.155 Å`
Energy of incident electrons is greater than the ionization energy of electron in `K- shell`, the `K- shell` electrons will be knocked off . Hence, characteristic X - ray spectrum will be obtained