Explanation

• The audible range of a normal human ear is 20 Hz to 20,000 Hz (20 kHz).
• Sounds below this range are called infrasound,
• Sounds above it are called ultrasound. 
• Lower limit: 20 Hz (deep rumbles)
• Upper limit: 20,000 Hz (high-pitched squeaks)

Additional information

• Adult change: The upper limit often drops to 15,000–17,000 Hz as people get older. 
• Unit of frequency: Hertz (Hz)

Last updated 27-07-2026 by NA

Explanation

• Short-sightedness is called Myopia.
• It is corrected by a concave lens.
• This lens is thin in the center and thick at edges.
• It helps light focus on the retina correctly.
• Without correction, distant objects look blurred.

Additional information:

• Long-sightedness is called Hypermetropia.
• It is corrected by a convex lens.
• This lens is thick in the center and thin at edges.
• It helps light focus on the retina properly.
• Without correction, near objects look blurred.

Last verified on 07-06-2026

Explanation

• Almost all the mass of an atom is concentrated in its nucleus.
• The nucleus contains protons and neutrons, which are much heavier than electrons.
• Electrons revolve around the nucleus but contribute very little to atomic mass.
• The nucleus is located at the center of the atom.
• Ernest Rutherford discovered the nucleus through the gold foil experiment in 1911.

Last verified on 09-05-2026

Explanation

In a concave mirror, the image size depends upon the:

• Position of the object relative to the mirror's focal point (f)
• Center of curvature(C)

Additional information

• Concave lenses are also known as diverging lenses. 

Last updated on 09-03-2026

Explanation

Explanation

Alpha (α) radiation consists of heavy, positively charged particles (alpha particles) that are emitted from the nucleus of an atom during certain types of radioactive decay.

Alpha particles are highly ionizing, meaning they can efficiently remove tightly bound electrons from atoms, resulting in the formation of ions.

Explanation

Bernoulli’s Principle explains that faster airflow over the wings creates lower pressure, producing lift that keeps the airplane in the air.

Explanation

Parsec (per sec) is an astronomical unit used to measure large distances between stars or galaxies.

1 parsec ≈ 3.26 light years.

Explanation

• Wavelength is the distance between two consecutive points on a wave that are in phase.
• It is typically denoted by the symbol λ (lambda).

Key Points:

• Time period (T) is the time taken by the wave to complete one oscillation.
• Frequency (f) is the number of oscillations per unit time.
• Amplitude (A) is the maximum displacement of the wave from its equilibrium position.

Explanation

A NOT gate, also known as an inverter.

It is a digital logic gate that negates the input signal.

If the input is "1", the output will be "0".

If the input is "0", the output will be "1".

The truth table for a NOT gate is:

Input | Output

-----|------

0 | 1

1 | 0