Explanation

• Because sound is just vibrating air, space has no air to vibrate and therefore no sound in a vacuum.
• Sound waves below 20 Hz are known as infrasound.
• Sound waves above 20 kHz are known as ultrasound.

Sound waves transmit a medium such as a gas, liquid, or solid.

• The speed of sound in air is about 343 meters per second.
• The sound travels at 1,481 m/s in water.
• The speed of sound in a vacuum is zero meters per second.

Last verified on 07-06-2026

Explanation

• Smog is a form of air pollution formed by smoke + fog.
• It mainly occurs in big cities due to vehicle and factory emissions.
• It reduces visibility and causes breathing problems.
• Smog is a serious environmental and health hazard.

Last verified on 06-06-2026

Explanation

• Oceans play the most important role in regulating Earth’s temperature and climate.
• They absorb heat from the Sun and distribute it across the planet.
• Ocean currents control weather patterns globally.
• They help maintain Earth’s temperature balance.

Last verified on 06-06-2026

Explanation

• Mangrove forests act as barriers against cyclones.
• Mangroves reduce erosion by trapping sediments, stabilizing the coastal zone and thus protecting the coast from storm surges and cyclones.
• Mangroves in Pakistan are found along the coastline of Sindh and Balochistan.

Last verified on 06-06-2026

Explanation

• Sea water contains a high amount of dissolved salts.
• Because of salinity, its freezing point is lower than fresh water.
• Fresh water freezes at 0°C, but saltwater freezes at a lower temperature.

Last verified on 01-06-2026