Identify the incorrect statement relating to deflections in an electric field of a stream of ionized radiation containing 𝛼 particles, 𝛽 particles, and 𝛾 rays. (A) The streams of 𝛼 particles and 𝛽 particles are separated. (B) 𝛽 particles are deflected less than 𝛼 particles. (C) 𝛼 particles are deflected in the opposite direction to 𝛽 particles. (D) An electric field creates a large deflection in the stream of 𝛽 particles. Or (E) 𝛾 rays are not deflected by an electric field.
Each of the statements relates to the deflection of a stream of ionized radiation in an electric field. The ionized radiation contains 𝛼 particles, 𝛽 particles, and 𝛾 rays. To identify which of the statements is incorrect, let’s start by comparing each type of radiation. An 𝛼 particle consists of two positively charged protons and two neutral neutrons. As both protons and neutrons have a mass of one unified atomic mass unit, an 𝛼 particle has a mass of four unified atomic mass units. And as an 𝛼 particle contains two positively charged protons and two neutral neutrons. Its overall charge is 2+.
A 𝛽 particle, more specifically, a 𝛽− particle, is a high-energy electron. Electrons or 𝛽− particles are significantly smaller than 𝛼 particles and have an approximate mass of one divided by 1800 unified atomic mass units. As 𝛽− particles are high-energy electrons, they have a charge of 1−. 𝛾 rays, also called 𝛾 radiation, are a form of electromagnetic radiation. 𝛾 rays do not have mass or charge.
Now that we know some of the properties of 𝛼 particles, 𝛽 particles and 𝛾 rays, let’s consider what happens when a stream of ionized radiation containing all three is passed through an electric field. As 𝛾 rays do not have a charge, they will not be affected by the electric field and will continue to travel along the same path. This means that answer choice (E) is a true statement. Since we are trying to identify the statement which is incorrect, we know that answer choice (E) cannot be the answer to this question.
𝛽− particles are negatively charged, so they should be attracted to the positively charged side of the electric field. And as their mass is so small, they will be strongly deflected by the electric field. This means that answer choice (D) is a true statement and cannot be the answer to this question. 𝛼 particles are positively charged, so they should be attracted to the negatively charged side of the electric field. The magnitude of the charge of an 𝛼 particle is two times greater than that of a 𝛽− particle. So, we might expect an 𝛼 particle to be deflected more than a 𝛽 particle in an electric field. However, the mass of an 𝛼 particle is over 7000 times greater than the mass of a 𝛽 particle.
As 𝛼 particles are much more massive than 𝛽 particles, they will be deflected to a lesser extent. We can see that upon passing through an electric field, the streams of 𝛼 particles and 𝛽 particles have been separated and the particles have been deflected in opposite directions. Thus, statements (A) and (C) are true and cannot be the answer to this question.
This leaves us with statement (B), which is false. 𝛽 particles are deflected more than 𝛼 particles in an electric field. Therefore, the incorrect statement relating to deflections in an electric field of a stream containing 𝛼 particles, 𝛽 particles, and 𝛾 rays is statement (B): 𝛽 particles are deflected less than 𝛼 particles.