Difficulty: Easy
Correct Answer: Gamma rays
Explanation:
Introduction / Context:
Radioactive substances and discharge tubes can emit several kinds of radiation. Some of these radiations are beams of particles with mass and charge, while others are waves of electromagnetic energy without rest mass. This question asks you to identify which listed radiation does not consist of material particles and instead is a form of electromagnetic radiation. Recognising the nature of each type is basic to nuclear physics and radiation safety.
Given Data / Assumptions:
Concept / Approach:
Each type of radiation can be classified as either particulate or electromagnetic. Alpha radiation consists of alpha particles, which are helium nuclei with two protons and two neutrons, so they are material particles. Beta radiation consists of fast moving electrons or positrons, which are also particles with mass. Anode rays, also called canal rays, are beams of positive ions in gas discharge tubes. Gamma radiation, on the other hand, is a form of electromagnetic radiation, similar to X rays but with higher energy, and consists of photons rather than massive particles. Therefore, gamma rays are the radiation that does not contain material particles.
Step-by-Step Solution:
Step 1: Recall that alpha rays are composed of alpha particles, which are helium nuclei containing protons and neutrons.
Step 2: Recall that beta rays originate from electrons or positrons emitted during nuclear beta decay, which have mass and charge.
Step 3: Recall that anode rays, or canal rays, were discovered in gas discharge tubes and consist of positively charged ions moving toward the cathode region.
Step 4: Recall that gamma rays are high frequency, high energy electromagnetic waves emitted from excited nuclei.
Step 5: Conclude that gamma rays are not beams of material particles but are massless photons, so they do not contain material particles.
Verification / Alternative check:
Experiments that measure mass and charge show that alpha particles have a definite mass about four times that of a proton and a positive charge of plus two. Beta particles have a mass equal to that of electrons and a negative or positive unit charge. Anode rays are observed to bend in electric and magnetic fields in ways consistent with positive ions of various masses. Gamma rays, in contrast, are affected differently in fields and show wave like properties such as diffraction and interference, with energies in the gamma region of the electromagnetic spectrum. These observations justify classifying gamma rays as electromagnetic radiation without rest mass.
Why Other Options Are Wrong:
Alpha rays are particulate because they consist of helium nuclei, which are massive and charged. Beta rays are also particulate since they are electrons or positrons, again with definite mass and charge. Anode rays are streams of positive ions in gas discharge tubes, so they are clearly material particles. None of these fit the description of radiation without material particles. Only gamma rays correspond to high energy photons with no rest mass and no electric charge.
Common Pitfalls:
A common confusion is between beta radiation and gamma radiation, since both can penetrate materials to some degree and are often mentioned together. Learners may also think that because gamma radiation comes from the nucleus, it must involve particles. To avoid confusion, remember that alpha and beta radiation involve ejected particles, while gamma radiation is a pure energy wave emitted when the nucleus moves from an excited state to a lower energy state. The key phrase to remember is that gamma rays are electromagnetic radiation, not matter beams.
Final Answer:
The radiation that does not contain material particles and is instead electromagnetic in nature is gamma rays.
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