Q. In a mass spectrometer used for measuring the masses of ions, the ions are initially accelerated by an electric potential V and then made to describe semicircular path of radius R using a magnetic field B. If V and B are kept constant, the ratio (charge on the ion/mass of the ion) will be proportional to
A) 1/R²
B) R²
C) R
D) 1/R
Explanation
[Solution from source] qV = ½mv² and R = mv/(qB) give R² = 2mV/(qB²), so q/m = 2V/(B²R²) ∝ 1/R². Answering 1/R ignores that v itself depends on q/m. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.