Question

Characteristic X-ray Emission is called Secondary Radiation. Why?

Answer 1

WHEN HIGH ENERGY ELECTRONS BEAM STRIKE THE METAL TARGET THEY KNOCKED OUT ELECTRON FROM THE INNER SHELL OF THE ATOMS. THESE ELECTRONS ARE CALLED PRIMARY ELECTRONS. AS VACANCY IS CREATED IN INNER SHELL,  ELECTRONS FROM THE OUTER SHELL (FROM HIGHER ENERGY STATE ) START JUMPING TO  FILL THE VACANCY IN INNER SHELL CREATED. THESE ELECTRON IS CALLED SECONDARY ELECTRONS. WHEN ELECTRONS JUMP FROM HIGHER ENERGY TO LOWER ENERGY STATE  THEY EMIT THEIR ENERGY AS A RADIATION. THESE RADIATION IS NOTHING BUT X-RAYS. SINCE X - RAYS IS GENERATED BY SECONDARY ELECTRONS THAT'S WHY IT IS CALLED SECONDARY RADIATION.