All Free Everyday Science MCQs with Answers

1621. What do we call when the sound of frequency will be below 20 Hz?

• A. Audio sounds
• B. Infrasonic
• C. Ultrasonic
• D. Supersonics

Explanation: Sound below 20 hertz is called infrasonic sound and is generally below the lower limit of human hearing. Ultrasonic sound is the opposite category, with frequencies above 20,000 hertz.

1622. Which colour of light is deviated least ________.

• A. Red
• B. Blue
• C. Violet
• D. Green

Explanation: Red light is deviated least in a prism because it has the longest wavelength and the lowest refractive index among the listed visible colours. Violet, with the shortest wavelength, deviates most.

1623. The S. I. unit of refractive index is _______?

• A. meter
• B. cm
• C. watt
• D. no unit

Explanation: Refractive index is a ratio of the speed of light in vacuum to its speed in a medium, so the units cancel. It is therefore dimensionless and has no SI unit.

1624. During which process of energy exchange does cold air displace warmer air?

• A. Convection
• B. Radiation
• C. Conduction
• D. None of these

Explanation: Cold air is denser, so it sinks and displaces warmer, less-dense air, producing convection currents. Radiation and conduction do not involve bulk movement of air.

1625. In general, good absorbents of electromagnetic radiation are also good___________?

• A. Radiators
• B. Conductors
• C. Insulators
• D. Semi Conductors

Explanation: A good absorber of radiation is generally also a good emitter, or radiator, of radiation. This is the basis of Kirchhoff’s law of thermal radiation.

1626. What method of energy transfer requires no medium for transfer?

• A. Radiation
• B. Convection
• C. Conduction
• D. A and B both

Explanation: Radiation transfers energy through electromagnetic waves and can travel through a vacuum, so it requires no material medium. Conduction and convection require matter.

1627. During which process does heat transfer occur because of density differences__________?

• A. Convection
• B. Radiation
• C. Conduction
• D. None of these

Explanation: Convection transfers heat through the movement of fluids caused by density differences: warmer, less-dense fluid rises while cooler, denser fluid sinks. Conduction does not involve bulk fluid motion.

1628. Heat of sun reaches the earth by ___________?

• A. Convection
• B. radiation
• C. Conduction
• D. None of these

Explanation: The Sun-to-Earth distance is essentially a vacuum, so neither conduction nor convection can carry the heat across it. Solar energy reaches Earth by electromagnetic radiation.

1629. For seeing objects at the surface of water from a submarine under water, the instrument used is ________?

• A. Periscope
• B. Telescope
• C. Kaleidoscope
• D. Spectroscope

Explanation: A periscope uses mirrors or prisms to let someone view objects above the water while remaining submerged. Telescopes magnify distant objects, whereas kaleidoscopes and spectroscopes serve different purposes.

1630. Escape velocity of a rocket fired from the earth towards the moon is a velocity to get rid of the _______?

• A. Centripetal force due to the earth's rotation
• B. Earth's gravitational pull
• C. Pressure of the atmosphere
• D. Moon's gravitational pull

Explanation: Escape velocity is the minimum speed needed to escape a body's gravitational field without further propulsion. For a rocket leaving Earth toward the Moon, the relevant pull initially is Earth's gravity, not atmospheric pressure or the Moon's weaker pull.