Question

Two particles having same charge and $KE$ enter at right angles into the same magnetic field and travel in circular paths of radii $2cm$ and $3cm$ respectively. The ratio of their masses is :

• A. $2:3$
• B. $3:2$
• C. $4:9$
• D. $9:4$

Answer 1

Answer: (C)

$4:9$

Radius of charged particle in magnetic field is,
$r=\frac{mv}{qB}$
$\frac{m{v}^2}{2}=K_e$
$r=\frac{\sqrt{2K_{e}m}}{qB}$
$r_1=\frac{\sqrt{2K_e{m}_1}}{qB}$
$r_2=\frac{\sqrt{2K_e{m}_2}}{qB}$
$\frac{4}{9}=\frac{m_1}{m_2}$