Explanation

• The velocity of a wave depends on its wavelength and frequency.
• Formula: v = λ × f, where λ is wavelength and f is frequency.
• This applies to sound waves, light waves, and water waves.
• Higher frequency or longer wavelength increases the wave’s velocity if the medium is constant.

Last verified on 17-03-2026

Explanation

• An echo is a sound that reflects off a surface and is heard again.
• It occurs when sound waves bounce back from a distant surface like a wall or mountain.
• Echoes are common in caves, valleys, and empty halls.
• The reflected sound is perceived after a short delay.

Last verified on 17-03-2026

Explanation

• Gravity pulls objects toward the center of the Earth.
• To lift or move an object against gravity, a force equal to or greater than gravitational force is needed.
• This force allows objects to rise or stay in motion vertically.

Last verified on 17-03-2026

Explanation

• When a marker is held and released, gravity pulls it downward.
• If there was an initial upward push, the upward force can be greater than the downward force momentarily.
• The marker accelerates until gravity slows it and pulls it back down.
• This explains the initial upward motion before falling.

Last verified on 17-03-2026

Explanation

• Total internal reflection occurs when light travels from a denser medium to a rarer medium.
• The angle of incidence must be greater than the critical angle for the two media.
• Light is completely reflected back into the denser medium instead of refracting.
• Common examples: optical fibers, diamonds, and mirages.

Last verified on 17-03-2026

Explanation

• The sky appears blue due to Rayleigh scattering of sunlight by the atmosphere.
• Shorter wavelengths like blue light scatter more than longer wavelengths (red, yellow).
• The scattered blue light reaches our eyes, making the sky appear blue.
• Red light is less scattered and passes through the atmosphere.

Last verified on 17-03-2026

Explanation

• Polyvinyl chloride (PVC) is a widely used synthetic polymer.
• It is a solid plastic material at room temperature.
• PVC is used in pipes, bottles, cables, and packaging.
• It is durable, lightweight, and resistant to corrosion.

Last verified on 17-03-2026

Explanation

• The primary colors are Red, Blue, and Green in the additive color system (used in screens, digital displays, and light).
• Mixing Red + Green = Yellow, Red + Blue = Magenta, Blue + Green = Cyan.
• Used in RGB model for TVs, computers, and digital devices.
• Example: Combining all three in full intensity produces white light.

Additional information:

• In subtractive color systems (like painting), the primary colors are Red, Yellow, Blue.

Last verified on 17-03-2026

Explanation

• Sand is primarily composed of silicon dioxide (SiO₂).
• It is a chemical compound made of silicon and oxygen atoms in a 1:2 ratio.
• SiO₂ is found in quartz, glass, and sand naturally.
• It is hard, chemically stable, and insoluble in water.

Last verified on 16-03-2026

Explanation

• Temperature is a physical quantity because it can be measured directly using a thermometer.
• It describes how hot or cold a body is without changing its chemical composition.
• Physical quantities are measurable properties like length, mass, volume, and temperature.
• Weight, force, and speed are derived quantities because they depend on mass, acceleration, or distance.

Last verified on 16-03-2026