Explanation

• Short-sightedness (myopia) can be corrected by wearing a concave lens.
• It is thinner in the center than at the edges.
• This lens disperses light rays, allowing them to focus correctly on the retina.

Explanation

Explanation

Question: A girl throws a small stone into a lake. Waves spread out from where the stone hits the water and travel to the bank of the lake. She notices that ten waves reach the side of the pond in a time of 5.0s. What is the frequency of the waves?

Answer: Frequency is defined as the number of waves (or cycles) per second. In this case, 10 waves reach the bank in 5 seconds, so:

Frequency = Number of waves / Time

= 10 waves / 5 s

= 2 waves/s

= 2.0 Hz

Explanation

Nuclear fusion is a process where two or more light nuclei (atomic nuclei with a small number of protons and neutrons) combine to form a single, heavier nucleus.

This process releases energy, as the resulting nucleus has a higher binding energy than the original nuclei.

Explanation

Nuclear fission is a process in which a heavy, unstable nucleus splits into two or more smaller nuclei, releasing energy and often additional particles like neutrons.

This process is the opposite of nuclear fusion, where smaller nuclei combine to form a heavier nucleus.

Explanation

The main source of energy in stars is nuclear fusion.

It is the process of combining atomic nuclei (usually hydrogen nuclei) to form a heavier nucleus, releasing vast amounts of energy in the process.

This energy is what makes stars shine.

Explanation

Question: A powder contains 100mg of a radioactive material that emits α-particles. The half-cycle of the isotope is five days. The mass of isotope that remains after ten days will be?

Answer: The half-life of the isotope is 5 days, which means that every 5 days, half of the remaining material decays. After 10 days, there will be two half-lives:

1. First half-life (5 days): 100mg → 50mg (half of the material decays)
2. Second half-life (next 5 days): 50mg → 25mg (half of theq remaining material decays)

So, after 10 days, 25mg of the original 100mg will remain.

Explanation

Gamma (γ) radiation consists of high-energy electromagnetic waves, such as X-rays or gamma rays, that travel in a straight line and are not affected by electric or magnetic fields.

Gamma radiation is a form of ionizing radiation and can travel several meters in air or several centimeters in dense materials before being absorbed.

Explanation

The radioactive decay equation shows a parent nucleus (91Pa^233) decaying into a daughter nucleus (92U^233) with the emission of a particle.

The parent nucleus has an atomic number of 91 (Protactinium), and the daughter nucleus has an atomic number of 92 (Uranium).

This increase in atomic number indicates that a beta particle (β) has been emitted.

Explanation

The particle that comprises two protons and two neutrons is an alpha particle (α).

Alpha particles are emitted from the nucleus of an atom during a type of radioactive decay called alpha decay or α-emission.