Explanation

• A quantum of energy of light (electromagnetic radiation) is called a photon.

• Photon is the smallest discrete packet (bundle) of energy.

• It carries energy proportional to its frequency (E = hf).

• Photons have no mass and travel at the speed of light.

• Light shows particle nature due to photons.

Last verified on 09-05-2026

Explanation

• Photoelectric emission stops when the frequency of incident light is below the threshold frequency of the metal.

• Below this minimum frequency, electrons cannot gain enough energy to escape the metal surface.

• Each metal has its own threshold frequency.

• This effect supports the quantum theory of light.

Last verified on 09-05-2026

Explanation

• Spring tides occur when the Earth, Moon, and Sun are in a straight line (aligned).

• This happens during New Moon and Full Moon phases.

• The gravitational pull of the Moon and Sun combines, producing very high and very low tides.

• Spring tides are not related to seasons like spring; the name refers to “jumping or rising” tides.

• They occur about twice a month.

Last verified on 09-05-2026

Explanation

• Natural gas is mainly transported through pipelines over long distances.

• Pipelines provide a safe, continuous, and cost-effective method of transport.

• For long overseas transport, natural gas is converted into LNG (Liquefied Natural Gas).

Last verified on 09-05-2026

Explanation

• Biomass energy is produced from organic matter such as plants, animals, and waste materials.

• It includes wood, crop residues, dung, and food waste.

• It is a renewable energy source because it can be replenished naturally.

• It releases energy when burned or converted into biogas or biofuels.

• It helps reduce waste and provides an alternative to fossil fuels.

Last verified on 09-05-2026

Explanation

• Laser light is intense because its light waves are coherent, meaning they remain in the same phase and travel together.

• Coherent waves combine their energy, producing a strong and focused beam.

• LASER stands for “Light Amplification by Stimulated Emission of Radiation.”

• Laser light differs from ordinary light because it is highly directional and monochromatic.

• Due to very little spreading, laser beams can travel long distances with high intensity.

Last verified on 09-05-2026

Explanation

• Isotones are atoms of different elements having the same number of neutrons.

• Their atomic numbers are different but neutron numbers remain equal.

• Example: Carbon-14 and Nitrogen-15 both have 8 neutrons.

• Isotones may have different chemical properties because they belong to different elements.

• The term “isotone” was introduced in nuclear chemistry studies.

Last verified on 09-05-2026

Explanation

• Beta radiation has intermediate penetrating power between alpha and gamma rays.

• Alpha rays have the least penetrating power, while gamma rays have the highest.

• Beta particles can pass through paper but are stopped by thin aluminum sheets.

• Beta radiation consists of fast-moving electrons or positrons.

• Ernest Rutherford classified alpha and beta radiations during radioactive studies.

Last verified on 09-05-2026

Explanation

• Almost all the mass of an atom is concentrated in its nucleus.
• The nucleus contains protons and neutrons, which are much heavier than electrons.
• Electrons revolve around the nucleus but contribute very little to atomic mass.
• The nucleus is located at the center of the atom.
• Ernest Rutherford discovered the nucleus through the gold foil experiment in 1911.

Last verified on 09-05-2026

Explanation

• Coal energy is considered suitable for base-load power generation because coal can be stored and supplied continuously.
• Base-load power means electricity supplied continuously to meet constant demand.
• Coal power plants can operate 24 hours a day.
• Major base-load energy sources: Coal, Nuclear, Hydroelectric, Natural Gas, Geothermal.
• China is the world’s largest producer and consumer of coal.

Last verified on 09-05-2026