Question

The ratio of specific charges of a proton and an alpha particle is?
(A)- 2:1
(B)- 1:2
(C)- 1:4
(D)- 1:1

Answer 1

Hint: Specific charge of a particle is defined as the ratio of the charge on the particle to the mass of the particle. Both proton and alpha particles are positively charged species.

Complete step by step solution:
Let’s look at the solution of the given question
- A proton is a positively charged species found in the nucleus of the atom.
- An alpha particle is a positively charged helium ion. It has 2 protons and 2 neutrons.
Now, we will calculate the required ratio.
- Let’s suppose the specific charge of proton be ‘p’
- Therefore, the specific charge on alpha particle will be equal to ‘2p’
(This is because alpha particles have 2 protons and 2 neutrons, but the neutrons are uncharged species and have mass nearly equal to protons.)
- Hence, the ratio of specific charge of a proton to an alpha particle is given by:
\[=\dfrac{p}{2p}\]
\[=\dfrac{1}{2}\]
So, the ratio of specific charge of a proton to an alpha particle is 1:2

Hence, the answer to the given question is option (B).

Additional information:
Protons are positively charged sub-atomic particles present in the nucleus of the atom. Neutrons are the neutral species present in the nucleus of the atom. The protons and neutrons are held together by strong nuclear forces.

Note: Students should read the question properly and see which term is given first for calculating ratio, proton or alpha particle. If the alpha particle is mentioned first then the required ratio will get inverted. The unit of specific charge is different from charge. The unit of charge is Coulombs whereas the unit of specific charge is $C\,K{{g}^{-1}}$.