Explanation

Explanation

Explanation

Explanation

Explanation

Explanation

During a thunderstorm, the Earth can have a net positive charge on its surface.

This is because the negatively charged clouds above the Earth induce a positive charge on the Earth's surface.

Explanation

Refraction is the change in the direction of light when it passes from one medium to another.

It is one of the most commonly observed natural phenomena of light.

Optical prisms and lenses involve refraction to redirect light, and so does the eyes of living beings.

Explanation

• Luminous objects are those that emit light of their own.
• Such as the sun, stars, light/electric bulbs, glowsticks, torch, lamps, candle, fire flies, lantern fish and neon tube.
• They produce their own light through various processes like incandescence, fluorescence, or bioluminescence.

Explanation

A thermos flask is designed to reduce heat transfer through all three methods:

• Conduction: The flask has a vacuum insulation, which eliminates conduction through the container.
• Convection: The flask's design and vacuum insulation prevent convective heat transfer.
• Radiation: The flask's reflective coating minimizes radiant heat transfer.

Explanation

The cooling fins at the back of a refrigerator are typically made of a black, rough surface to maximize heat radiation. This design:

• Increases the surface area for heat transfer
• Absorbs heat from the surrounding air
• Emits heat more efficiently due to the rough surface