What is the mass of a positron?
A. Equivalent to the sum of a neutron and an electron
B. Equivalent to a proton
C. Equivalent to a neutron
D. Equivalent to an electron

Hint: To answer the given question, we need to know the fundamentals of a positron. Positron is basically a positive electron as the name describes. From this information, we can find the mass of a positron.

Complete step by step answer:
Let us first define what is positron.
The positron or antielectron can be defined as the antiparticle or the antimatter counterpart that is present in the electron. The positron has an electric charge of +1 e, a spin of $\dfrac{1}{2}$, and will have the same mass as an electron. If a situation arises where the positron collides with an electron, then annihilation will occur.
Hence, we can say that positive electron, positively charged subatomic particle having the same mass and magnitude of charge as the electron and constituting the antiparticle of a negative electron. So, the mass of a positron is equivalent to that of an electron.
Therefore, the correct answer is Option D.

Positrons are emitted in the positive beta decay of a proton rich (it is also neutron deficient) radioactive nuclei and are formed in pair production. In such a situation, the energy of a gamma ray in the field of a nucleus is converted into an electron-positron pair.

Additional Information:
Positrons emitted from man-made radioactive sources are used in various medical diagnoses. One such medical diagnosis technique is known as positron emission tomography or PET.

Note: We should know that positron is a stable particle in a vacuum. Since they are stable in vacuum, positrons will quickly react with the electrons of ordinary matter by annihilation to produce gamma radiation.