Consider the following particles :
(A) Proton
(B) \( \alpha \) particle
(C) Electron
For charge to mass ratio of the above particles we can say :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → \( (C) \gt (A) \gt (B) \)
Compare the specific charge \( q/m \) of each particle, using the proton charge \( e \) and the proton mass \( m_p \) as units.
\( \text{Proton: } q/m = e/m_p \)
\( \alpha\text{ particle: } q/m = 2e/(4m_p) = 0.5\,(e/m_p) \)
\( \displaystyle \text{Electron: } \frac{q}{m} = \frac{e}{m_e} = \frac{e}{m_p/1836} = 1836\,\frac{e}{m_p} \)
The electron is about 1836 times lighter than the proton with the same size of charge, so it has by far the largest \( q/m \). The alpha particle has twice the charge but four times the mass of the proton, so its \( q/m \) is half that of the proton.
\( (C) \gt (A) \gt (B) \)