Question

A beam of electrons striking a copper target produces X-rays.Its spectrum is as shown. Keeping the voltage same if the copper target is replaced with a different metal, the cut-off wavelength and characteristic lines of the new spectrum will change in comparision with old as :

• A. Cut-off wavelength will remain unchanged while characteristic lines will be different.
• B. Both cut-off wavelength and characteristic lines will remain unchanged.
• C. Both cut-off wavelength and characteristic lines will be different.
• D. Cut-off wavelength will be different while characteristic lines will remain unchanged.

Answer 1

The correct option is A Cut-off wavelength will remain unchanged while characteristic lines will be different.

Cut- off wavelength of emitted X-rays depends on maximum kinetic energy of incident electrons on the target and is independent of nature of target. The characteristic lines depend on nature of material of target.