Explanation

• The frequency of a wave remains unchanged when it passes from one medium into another.
• Wave speed decreases when a wave enters a denser medium.
• Wavelength also decreases because wave speed changes while frequency remains constant.

Last verified on 31-10-2026

Explanation

• Power is the rate of doing work or the rate at which energy is transferred.
• It is a scalar quantity (has magnitude only).
• It shows how quickly work is done.
• The SI unit of power is the Watt (W).
• 1 Watt = 1 Joule per second (1 W = 1 J/s).

Additional information:

• Formula: P = W/t = E/t
• SI Base Unit: kg·m²·s⁻³
• Dimension Formula: ML²T⁻³
• James Watt is the scientist after whom the Watt unit is named.

Last verified on 09-07-2026

Explanation

• Displacement is the straight-line change in position from an initial point to a final point.
• It is a vector quantity, having both magnitude and direction.

Last verified on 31-10-2026

Explanation

• Newton's second law defines force as the product of mass and acceleration.
• The net force acting on an object determines its acceleration.
• It also explains that force is equal to the rate of change of momentum.

Last verified on 31-10-2026

Explanation

• At the center of the Earth, g = 0.
• Gravity from all directions cancels out at the center.
• So net gravitational force becomes zero.
• An object would feel weightless there.
• This is due to symmetrical distribution of Earth's mass.
• Earth’s surface gravity: 9.8 m/s²

Last verified on 17-06-2026

Explanation

• All electromagnetic waves travel through a vacuum at 3x10^8 m/s.
• This is the speed of light (c).
• Radio waves, microwaves, visible light, X-rays and gamma rays all have the same speed in vacuum.

Last verified on 31-10-2026

Explanation

• Earth's magnetic field varies in both strength (magnitude) and direction from place to place.
• Its direction changes with geographic location and is not the same at the magnetic equator and poles.
• Its strength is generally weaker near the magnetic equator and stronger near the magnetic poles.

Last verified on 31-10-2026

Explanation

• The correct sentence is: “The director of human resources is interviewing applicants.”
• The singular subject “The director” agrees with the singular verb “is.”
• “The directors” is plural and would require the verb “are.”

Last verified on 31-10-2026

Explanation

• The correct sentence is: “The world is facing a serious energy problem.”
• The word “facing” needs the helping verb “is” in this sentence.

Last verified on 31-10-2026

Explanation

• The correct phrase is “galloping inflation”, which refers to a very high and rapidly increasing rate of inflation.
• Moderate inflation is relatively manageable, while galloping inflation creates serious economic instability.
• Policymakers become concerned because it reduces purchasing power and increases uncertainty.

Last verified on 31-10-2026