Explanation

• Ole Rømer was the first person to experimentally demonstrate that light has a finite speed in 1676.
• He used observations of Jupiter’s moon Io to estimate the speed of light.

Additional information:

• The modern accepted speed of light in vacuum is 299,792,458 m/s.

Last verified on 07-10-2026

Explanation

• Smog is a combination of smoke and fog.
• The word smog is formed from smoke + fog.
• It is a type of air pollution that reduces visibility and can harm human health.
• Smog is commonly associated with vehicle emissions and industrial pollutants.

Last verified on 06-10-2026

Explanation

• The SI unit of power is the watt (W). 
• A watt is equal to one joule of work done per second. 
• Symbol: W
• Definition: 1 watt = 1 joule per second
• Named after: James Watt

Last verified on 05-10-2026

Explanation

• Silviculture is the science and practice of establishing, growing, managing, and harvesting forest trees.
• It deals with the growth and development of forests.
• It aims to maintain healthy and productive forest resources.

Additional information:

• Forestry: Science and management of forests and forest resources.
• Agriculture: Cultivation of crops and rearing of animals.
• Arboriculture: Cultivation and management of individual trees and shrubs.

Last verified on 05-10-2026

Explanation

• In SONAR, the wavelength of the sound wave does not change simply because the submarine is farther away.
• Wavelength depends on the frequency of the sound and its speed in the medium, not on the distance traveled.

Additional information:

• SONAR: Sound Navigation and Ranging
• It uses sound waves to detect and locate underwater objects.

Last verified on 05-10-2026

Explanation

• Sericulture is the farming or rearing of silkworms for the production of silk.
• The most commonly cultivated silkworm is Bombyx mori.
• Silkworms feed mainly on mulberry leaves and produce silk fibers to form their cocoons.

Additional information:

• Apiculture: Rearing of honeybees for honey and other products.
• Agriculture: Cultivation of crops and raising of animals.
• Pisciculture: Farming or breeding of fish.

Last verified on 05-10-2026

Explanation

• Community consists of populations of different species living and interacting in the same area.

Additional information:

• Population → members of the same species
• Ecosystem → community + non-living environment
• Biosphere → all ecosystems on Earth

Last verified on 05-10-2026

Explanation

• A black box is a flight recorder used in aircraft.
• It records important flight data and cockpit audio.
• It helps investigators determine the causes of aircraft accidents or incidents.
• The two main types are Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR).

Last verified on 05-10-2026

Explanation

• Watt (W) is the SI unit of power, while kilowatt (kW) is also a unit of power.
• 1 kilowatt = 1,000 watts.
• Power indicates the rate at which energy is used or transferred.

Additional information:

• Kilowatt-hour (kWh) is a unit of electrical energy.

Last verified on 05-10-2026

Explanation

• Polyethylene (PE) is one of the most widely used plastics in the world.
• Because it is lightweight, durable, chemically resistant, and relatively inexpensive.
• It is commonly used to make plastic bags, bottles, containers, packaging films, and household products.
• Polyethylene is produced from ethylene (ethene) through polymerization.

Last verified on 05-10-2026