Explanation

The K orbit, also known as the first electron shell.

• It can hold a maximum of 2 electrons.

The L orbit, also known as the second electron shell.

• It can hold a maximum of 8 electrons.

The M orbit, also known as the third electron shell.

• It can hold a maximum of 18 electrons.

Last verified on 19-03-2026

Explanation

• The mass number (A) is the sum of protons and neutrons present in the nucleus of an atom.
• It is a measure of the total number of nucleons (protons and neutrons) in the nucleus.
• It helps determine the atomic mass and distinguishes isotopes of an element.

Last verified on 19-03-2026

Explanation

• Halazone tablets are used to purify drinking water by killing bacteria and pathogens.
• Commonly used in emergencies, military, or travel situations where safe water is unavailable.
• Halazone tablets can purify 1 liter of water in about 5–10 minutes.

Last verified on 19-03-2026

Explanation

• About 97.5% of the water on Earth is saltwater, found in oceans, seas, and salt lakes.
• The remaining 2.5% is freshwater, found in rivers, lakes, wetlands, and underground aquifers.

Last verified on 19-03-2026

Explanation

• If an object absorbs all seven colors of light (i.e., all the wavelengths of visible light), it appears black.
• This is because no light is being reflected, and our eyes perceive the absence of light as black.
• When an object reflects all the component colors of light, it appears white.

Last verified on 18-03-2026

Explanation

• Stars produce energy by combining lighter nuclei into heavier nuclei in their cores.
• In the core of a star, hydrogen nuclei fuse to form helium.
• This process releases a huge amount of energy in the form of light and heat.
• It is the primary source of a star’s energy and sustains its radiation for billions of years.

Last verified on 17-03-2026

Explanation

• The velocity of a wave depends on its wavelength and frequency.
• Formula: v = λ × f, where λ is wavelength and f is frequency.
• This applies to sound waves, light waves, and water waves.
• Higher frequency or longer wavelength increases the wave’s velocity if the medium is constant.

Last verified on 17-03-2026

Explanation

• An echo is a sound that reflects off a surface and is heard again.
• It occurs when sound waves bounce back from a distant surface like a wall or mountain.
• Echoes are common in caves, valleys, and empty halls.
• The reflected sound is perceived after a short delay.

Last verified on 17-03-2026

Explanation

• Total internal reflection occurs when light travels from a denser medium to a rarer medium.
• The angle of incidence must be greater than the critical angle for the two media.
• Light is completely reflected back into the denser medium instead of refracting.
• Common examples: optical fibers, diamonds, and mirages.

Last verified on 17-03-2026

Explanation

• Ions are charged particles formed when an atom gains or loses electrons.
• Loss of electrons creates a positively charged ion (cation).
• Gain of electrons creates a negatively charged ion (anion).

Last verified on 17-03-2026