Question

A proton and an $\alpha -$particles enters in a uniform magnetic field with same velocity, then ratio of the radii of path describe by them

• A. $1 : 1$
• B.
• C.
• D. None of these

Answer 1

Answer: (B)

Answer 2

By using $r = \frac { m v } { q B }$ ; $v \rightarrow$same, $B \rightarrow$ same

$\Rightarrow$ $r \propto \frac { m } { 2 }$ $\Rightarrow$ $\frac { r _ { p } } { r _ { \alpha } } = \frac { m _ { p } } { m _ { \alpha } } \times \frac { q _ { \alpha } } { q _ { p } }$ $= \frac { m _ { p } } { 4 m _ { p } } \times \frac { 2 q _ { p } } { q _ { p } } = \frac { 1 } { 2 }$