Explanation

• Sound cannot travel through a vacuum because there are no particles to carry sound vibrations.
• Sound needs a medium such as a solid, liquid, or gas to travel.
• Since space is nearly a vacuum, sound cannot be heard there.
• The speed of sound in a vacuum is 0 m/s.

Additional information:

• Infrasound: Below 20 Hz
• Audible sound: 20 Hz – 20,000 Hz (20 kHz)
• Ultrasound: Above 20 kHz
• Speed of sound in air: 343 m/s
• Speed of sound in water: 1,481 m/s

Last verified on 07-06-2026

Explanation

• Vitamin D is essential for healthy bones.
• Its deficiency leads to Rickets in children and Osteomalacia in adults.
• Sunlight is the best natural source of Vitamin D.

Additional information:

Deficiency effects:

• Bone pain
• Weak bones
• Skeletal deformities

Other Vitamin Deficiencies:

• Vitamin A: Night blindness
• Vitamin C: Scurvy
• Vitamin B7 (Biotin): Hair fall

Last verified on 17-01-2026

Explanation

• Solids → fastest sound speed
• Liquids → medium speed
• Gases → slowest speed

Steel is more elastic and dense.

• Steel ≈ 5000 m/s
• Air ≈ 332 m/s
• Water ≈ 1500 m/s

Last verified on 11-04-2026

Explanation

• Rainfall is measured using a Rain Gauge.
• It collects rainwater and measures it in millimeters (mm).
• Widely used in weather forecasting and meteorology.
• Helps in studying climate and agriculture patterns.

Last verified on 31-03-2026

Explanation

• A carbon microphone does not depend on the magnetic effect of current.
• Based on the variation of electrical resistance
• It converts sound vibrations into electrical signals 

Additional information 

Devices like electromagnets, electric bells, and ammeters work due to the magnetic effect of current.

Last updated on 09-03-2026

Explanation

"Equinox"  means Equal duration of day and night.

The time or date (twice each year) at which the sun crosses the celestial equator 

During the equinoxes, solar declination is 0°

The September equinox is called the autumnal or fall equinox on 23 September

The March equinox is called the vernal or spring equinox on 19 March or as late as 21 March

Explanation

H5N1 is a type of influenza virus

Causes a highly infectious

Also known as avian influenza.

Occurs mainly in birds, is highly contagious among birds, and can be deadly, especially in domestic poultry

Explanation

Herodotus is called the Father of History.

Additional information:

• Born: 484 BC, Halicarnassus (modern-day Bodrum, Turkey)
• Died: 425 BC, Thurii, Italy
• Famous Work: Histories – detailed accounts of Greco-Persian Wars
• Contribution: First to collect, verify, and narrate historical events systematically

Last verified on 18-01-2026

Explanation

• Sedimentary rocks are rocks formed by the deposition and compression of sediments over time.
• Also called stratified rocks because they are formed in layers (strata).
• Often porous, meaning they have small holes (pores) that can contain water or other fluids.

Additional information:

• Cover about 75% of the Earth's surface.
• Examples: Sandstone, Limestone, Shale.
• Usually softer and less dense than igneous rocks.

Explanation