Explanation

Lasers operate on the principle of stimulated emission, proposed by Einstein.

In stimulated emission, an incoming photon stimulates an excited atom to drop to a lower energy level, releasing a new photon.

This new photon has:

• Same energy
• Same wavelength
• Same polarization
• Same phase and direction
• as the photon that stimulated it.

Because of this process, all photons in a laser beam are coherent, monochromatic, and travel in the same direction — a unique property of laser light.

Explanation

Explanation

• Television signals cannot be received ordinarily beyond a particular distance due to the curvature of the earth.

Key Points

• Signal waves travel in a straight line from the transmitting antenna to the receiving antenna. The signal transmitted from a TV tower cannot be received beyond a certain distance because the surface of the Earth is curved.
• This is due to, after going a certain distance the frequency of television signals decreases while their wavelength increases.
• Signal waves transmitted from a transmitter get absorbed or blocked by the curvature of Earth and are not received. 

Additional Information

• Signal:
  • Information converted in electrical form and suitable for transmission is called a signal.
  • Signals can be either analog or digital.

Explanation

The friction between the car's tires and the road provides the necessary centripetal force that keeps the car moving in a circular path.

This frictional force acts towards the center of the circular path, allowing the car to change direction without sliding out.

Explanation

When meteors enter Earth’s atmosphere, they burn with light due to friction produced by rapid motion.

The high-speed entry causes the meteor to compress the air in front of it, creating intense heat and resulting in a visible streak of light.

Explanation

The output of an OR gate will be high when any of the inputs is high.

An OR gate outputs a high signal if at least one input is high.

Explanation

A network containing one or more sources of EMF is known as an Active Network.

Active networks include elements like batteries or generators that provide energy to the circuit.

Explanation

The materials are called conductors if the electrons can move easily.

Conductors, like copper and aluminum.

It have low resistance and allow electrical current to flow freely through them.

Explanation

• The electricity used in homes and schools is typically Alternating Current (AC).
• It is the type of electric current that periodically changes direction.
• This is the type of current provided by power plants and distributed through the grid.

Explanation

• Car brakes are typically hydraulic systems, not pneumatic systems.

The examples of pneumatic systems:

• Spray gun: uses compressed air to atomize and spray paint or other materials.
• Bicycle pump: uses compressed air to inflate tires.
• Vacuum cleaner: uses compressed air to create suction and lift dust and debris.