Explanation

• The audible range of a normal human ear is 20 Hz to 20,000 Hz (20 kHz).
• Below 20 Hz: Infrasound
• Above 20 kHz: Ultrasound
• Unit of frequency: Hertz (Hz)

Last verified on 23-06-2026

Explanation

• The density of gases increases when pressure is increased because gas molecules come closer together.
• Density is the mass per unit volume of a substance.
• When pressure increases, the volume of gas decreases (at constant temperature), causing density to increase.
• This relationship follows Boyle’s Law.

Last verified on 21-06-2026

Explanation

• The movement of water from higher water potential to lower water potential is called osmosis.
• It occurs through a semi-permeable membrane.
• Only water molecules move in osmosis.
• It is a passive process (no energy required).

Last verified on 18-06-2026

Explanation

• The instrument used to measure temperature is called a thermometer.
• A thermometer shows how hot or cold an object or place is.

Additional information:

• Barometer measures air pressure.
• Hygrometer measures humidity (moisture in air).

Last verified on 16-06-2026

Explanation

• The Sun is the ultimate and main source of energy on Earth.
• It provides energy through solar radiation (light and heat).
• All forms of energy on Earth directly or indirectly come from the Sun.
• It supports life, climate, and ecosystems on Earth.

This energy is then converted into various forms, such as:

• Thermal energy (heat)
• Kinetic energy (wind, water currents)
• Electrical energy (generated from solar panels)
• Chemical energy (fossil fuels, biomass)
• Biological energy (food chains, ecosystems)

Last verified on 16-06-2026