Q. Given below are two statements about X-ray spectra of elements : Statement (I) : A plot of $\sqrt\nu$ ($\nu$ = frequency of X-rays emitted) vs atomic mass is a straight line. Statement (II) : A plot of $\nu$ ($\nu$ = frequency of X-rays emitted) vs atomic number is a straight line. In the light of the above statements, choose the correct answer from the options given below :
A) Both Statement I and Statement II are true
B) Statement I is false but Statement II is true
C) Both Statement I and Statement II are false
D) Statement I is true but Statement II is false
Explanation
[Solution by Dr. Abubacker] Moseley's law is $\sqrt\nu=a(Z-b)$: $\sqrt\nu$ is linear in the atomic number $Z$, not in atomic mass, so Statement I is false. $\nu$ against $Z$ is a parabola, not a straight line, so Statement II is false. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.