Video: Applying Knowledge of the Nature of Gamma Rays and Their Detection with a Geiger Counter

For statements I and II, state for each if they are true or false. I) Gamma rays can be detected by a Geiger counter. II) Gamma rays are electrically charged. If both are true, state if II is a correct explanation for I.

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Video Transcript

For statements I and II, state for each if they are true or false. I) Gamma rays can be detected by a Geiger counter. II) Gamma rays are electrically charged. If both are true, state if II is a correct explanation for I.

Gamma rays, which you often see indicated by the Greek letter 𝛾, are a form of electromagnetic radiation. Gamma rays are very high energy. They’re higher in energy than X-rays on the electromagnetic spectrum. And they have a wavelength of about 10 to the minus 12 meters.

Because gamma rays are simply a form of electromagnetic radiation, they have no mass and no charge. Gamma ray emission is really common in nuclear reactions and often happens alongside other forms of radioactive emissions, like alpha and beta decay. Gamma emission generally occurs in nuclear reactions because the nucleus is in a very-high-energy excited state. And it will release gamma rays to release energy to return to the ground state.

Unlike alpha and beta decay, where the mass number or the atomic number change as a result of the nuclear reaction. Since gamma rays have no mass and no charge, the mass number and the atomic number remain unaffected by the emission of a gamma ray.

In addition to nuclear reactions, gamma rays are also emitted when a particle and an antiparticle annihilate each other. Such as when an electron and a positron combine, which will produce two gamma rays. This reaction is used in positron emission tomography, or PET. Which is a medical imaging technique where a small amount of a positron emitter is injected into the body, where it travels into the tissues, combines with electrons, and emits small amounts of gamma radiation. This technique can be used to image cancer cells and follow metabolic processes in the body.

Statement I of this question asked us if gamma rays can be detected by a Geiger counter. A Geiger counter is a tool that’s used to measure the amount of radiation. It works by first collecting emissions from a radioactive sample. The collected emissions will then strike argon atoms that are inside the counter, causing the argon atoms to be ionized. So we have positively charged argon atoms and electrons. These electrons and ions that are produced as a result of the radiation running into the argon atoms are then collected and measured. This will cause the counter to increase and in some Geiger counters will produce an audible click.

Geiger counters detect all forms of ionizing radiation, which is radiation that is energetic enough to ionize atoms or molecules that it encounters. Gamma radiation is very high in energy and is capable of ionizing atoms or molecules. So this statement is true.

Statement II says that gamma rays are electrically charged. As we’ve discussed, gamma rays are a form of electromagnetic radiation that’s very high in energy. So it has no mass and no charge. Since it has no charge, gamma rays can’t be electrically charged. So statement II is false.

Since statement II is false, we don’t have to answer the last part of the question.

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