In This post you will get answer of Q.
A doubly ionised $He^{+2}$ atom travels at rightist angles to a magnetic field of induction 0.4 T with a velocity, of $10^5ms^{-1}$ describing a circle of radius r. A proton travelling with same speed in same direction in the same field will describe a circle of radius
Solution:
$r= frac{mv}{Bq}$
Solution: