A proton and an `alpha-`particle enter a uniform magnetic field moving with the same speed. If the proton takes `25 mu s` to make 5 revolutions, then the periodic time for the `alpha-` particle would be

Options

A. `50 musec`
B. `25 mu sec`
C. `10 mu sec `
D. `5 mu sec `

Answer

C

Explanation

Time taken by proton to make one revolution
`=25/5 = 5mu` sec .
As `T = (2pim)/(qB) , " so " T_2/T_1 =m_2/m_1 xx(q_1)/(q_2)`
or `T_2 = T_1 (m_2q_1)/(m_1 q_2) = (5xx4m_1)/m_1 xxq/(2q)=10 mu sec`.