Question 1

What is the speed of light in vacuum according to modern physics?

Accepted Answer

The speed of light in vacuum is approximately 3 × 10⁸ meters per second (m/s), or more precisely 299,792,458 m/s. This is a fundamental constant in physics, denoted by the symbol 'c'.

Question 2

Which physicist formulated the law of universal gravitation?

Accepted Answer

Sir Isaac Newton formulated the law of universal gravitation in the late 17th century. This law states that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Question 3

Which scientist formulated the law of universal gravitation?

Accepted Answer

Sir Isaac Newton formulated the law of universal gravitation in the late 17th century. This law states that every mass attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.

Question 4

Which scientist is credited with the invention of the electric light bulb?

Accepted Answer

Thomas Alva Edison is credited with inventing the practical incandescent electric light bulb in 1879. While other scientists like Joseph Swan and Humphry Davy experimented with electric light earlier, Edison developed the first commercially viable and long-lasting incandescent bulb.

Question 5

Which physical quantity is measured in Hertz (Hz)?

Accepted Answer

Hertz (Hz) is the SI unit of frequency, which measures the number of cycles or oscillations per second. It is named after Heinrich Hertz, a German physicist who discovered electromagnetic waves.

Question 6

What is the SI unit of temperature?

Accepted Answer

The SI unit of temperature is the Kelvin (K), named after Lord Kelvin (William Thomson). Unlike Celsius or Fahrenheit, Kelvin is an absolute temperature scale where 0 K represents absolute zero, the lowest possible temperature.

Question 7

What is the SI unit of energy?

Accepted Answer

The Joule (J) is the SI unit of energy, work, and heat. One Joule equals one Newton-meter (1 J = 1 N·m), representing the energy transferred when a force of one Newton acts over a distance of one meter.

Question 8

Which of the following statements about friction is correct?

Accepted Answer

Friction is a force that opposes the relative motion between two surfaces in contact. It acts in the direction opposite to the motion and depends on the normal force and the nature of the surfaces.

Question 9

What is the SI unit of force?

Accepted Answer

The SI unit of force is the Newton (N), named after Sir Isaac Newton. One Newton is defined as the force required to accelerate a mass of one kilogram at a rate of one metre per second squared (F = ma).

Question 10

Which of the following is the SI unit of electric current?

Accepted Answer

The SI unit of electric current is the Ampere (A), named after French physicist André-Marie Ampère. It is defined as the flow of one coulomb of charge per second.

Question 11

What is the SI unit of force?

Accepted Answer

The Newton (N) is the SI unit of force, named after Sir Isaac Newton. One Newton is the force required to accelerate a mass of one kilogram at one meter per second squared (F = ma).

Question 12

Which of the following is an example of a renewable source of energy?

Accepted Answer

Renewable energy sources are those that can be replenished naturally and are sustainable over long periods. Solar energy, wind energy, hydroelectric power, and geothermal energy are all examples of renewable sources. Coal, oil, and natural gas are non-renewable fossil fuels.

Question 13

Which of the following statements about pressure is correct?

Accepted Answer

Pressure is defined as force per unit area (P = F/A). It is measured in Pascals (Pa) in the SI system. Pressure increases with greater force and decreases with larger area. This principle explains why sharp objects (small area) exert more pressure than blunt objects (large area) with the same force.

Question 14

Which of the following is the SI unit of electric current?

Accepted Answer

The SI unit of electric current is Ampere (A), named after French physicist André-Marie Ampère. It measures the flow of electric charge per unit time. One Ampere equals one Coulomb per second.

Question 15

A person uses a concave mirror to shave or apply makeup because concave mirrors produce:

Accepted Answer

Concave mirrors are converging mirrors. When an object is placed between the focal point and the mirror (within the focal length), a concave mirror produces a virtual, erect, and magnified image. This magnification helps in detailed grooming tasks.

Question 16

When light passes from a denser medium (like glass with refractive index 1.5) to a less dense medium (like air with refractive index 1.0), the light ray bends:

Accepted Answer

According to Snell's Law (n₁ sin θ₁ = n₂ sin θ₂), when light travels from a denser to a less dense medium, the refracted ray bends away from the normal. This is because the light speeds up when entering the less dense medium.

Question 17

A sound wave travels through air at approximately 340 m/s at room temperature (20°C). If a person hears an echo 2 seconds after shouting, what is the approximate distance to the reflecting surface (wall/cliff)?

Accepted Answer

Sound travels to the reflecting surface and back to the person. Total distance = speed × time = 340 m/s × 2 s = 680 m. Since this is the round-trip distance, the distance to the reflecting surface = 680 m ÷ 2 = 340 meters.

Question 18

Which of the following phenomena best explains why a person feels lighter when standing in an elevator moving downward with acceleration?

Accepted Answer

When an elevator accelerates downward, the normal force (N) exerted by the floor on the person decreases because N = m(g − a), where a is the downward acceleration. This reduced normal force creates the sensation of being lighter, even though actual weight (mg) remains constant.

Question 19

Which of the following best describes the phenomenon of refraction of light?

Accepted Answer

Refraction is the bending of light when it passes from one medium to another with a different optical density. This occurs because light travels at different speeds in different media, causing the light ray to change direction at the interface.

Question 20

What is the relationship between frequency and wavelength of a wave in the same medium?

Accepted Answer

Frequency and wavelength are inversely proportional in the same medium. This relationship is expressed as: v = f × λ, where v is the wave velocity (constant in a given medium), f is frequency, and λ is wavelength. Therefore, if frequency increases, wavelength decreases, and vice versa.

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60-Second Revision — Physics — Everyday Concepts