Explanation

• Density is the mass per unit volume of a substance.
• Density is calculated by dividing the mass of a substance by its volume.
• The SI unit of density is kilogram per cubic metre (kg/m³).

Last verified on 25-10-2026

Explanation

• Light travels at approximately 300,000 kilometres per second in a vacuum.
• While sound travels through air at about 343 metres per second at 20°C.
• Lightning produces a flash of light and heats the surrounding air rapidly, causing the thunder we hear.
• Light reaches our eyes almost instantly over ordinary storm distances, whereas sound takes longer to reach our ears.

Last verified on 22-10-2026

Explanation

• Intermediate-focus earthquakes: occur at depths of 70–300 km.

Additional information:

• Shallow-focus earthquakes: occur at depths of 0–70 km.
• Deep-focus earthquakes: occur at depths of 300–700 km.

Last verified on 22-10-2026

Explanation

• GIS (Geographic Information System) is a computer-based system used to collect, store, analyze, and display geographically referenced data.
• Its basic output is often a map that presents spatial information visually.
• GIS maps can show roads, buildings, rivers, land use, population distribution, and service locations.
• GIS also produces tables, statistics, reports, and spatial measurements, depending on the analysis.

Last verified on 21-10-2026

Explanation

• The lightning conductor or rod used for protecting buildings from lightning is made of copper.
• A lightning conductor is a metal rod installed at the highest point of a building to provide a safe path for lightning current to reach the ground.
• Copper is commonly used.
• Because it is an excellent electrical conductor.
• It has good resistance to corrosion.

Additional information:

• Light rod was invented by Benjamin Franklin in the 18th century.

Last verified on 21-10-2026