What is Radioactivity — Reading Comprehension

Radioactivity is a process where unstable atomic nuclei lose energy by emitting radiation. This process, known as radioactive decay, occurs because the nucleus of an atom has an imbalance of protons and neutrons, making it unstable. To achieve a more stable state, the atom releases particles and energy. This is a natural, spontaneous process that cannot be stopped or sped up. The three most common types of radiation emitted are alpha, beta, and gamma. An alpha particle consists of two protons and two neutrons and can be stopped by a sheet of paper. A beta particle is a high-speed electron that can pass through paper but is stopped by a thin sheet of aluminum. Gamma radiation is a form of high-energy light (like X-rays) with no mass or charge. It is the most penetrating type and requires thick lead or concrete to block it.

The rate at which a radioactive substance decays is measured by its half-life. Half-life is the time it takes for half of the radioactive atoms in a sample to decay. For example, if a substance has a half-life of 100 years, after 100 years, half of the original material will have decayed. After another 100 years (200 years total), half of the remaining material will have decayed, leaving one-quarter of the original amount. This concept is crucial for understanding how long radioactive materials remain dangerous.

Radioactivity has numerous real-world applications, from medicine to geology. In medicine, doctors use radioactive materials, or radiopharmaceuticals, to diagnose diseases by creating images of internal organs and to treat cancer by targeting and destroying malignant cells. In geology, scientists use a process called radiometric dating to determine the age of rocks and fossils by measuring the decay of radioactive isotopes within them. This allows us to understand the history of our planet and the life that has existed on it.

Fun Fact: A banana is naturally radioactive because it contains potassium-40, a radioactive isotope. However, the radiation dose is so small that it is completely harmless.

What is the fundamental cause of radioactivity?

Which type of radiation is the most difficult to block and requires thick lead or concrete?

What does the term "half-life" refer to?

If a radioactive substance has a half-life of 50 years, what fraction of the original material will remain after 100 years?

According to the passage, which application of radioactivity helps scientists determine the age of ancient fossils?

Based on the passage, what is the main idea of the text?

Which type of radiation is composed of two protons and two neutrons?

A scientist is studying a new substance with a half-life of 25 years. If they start with 80 grams of the substance, how much will be left after 75 years?