Explanation

• The average distance covered by an alpha particle in air before losing its ionizing power is called its range.
• Alpha particles lose energy continuously while moving through air.
• They stop ionizing after traveling a certain distance.
• This stopping distance is not straight-line path always due to collisions.

Last verified on 05-06-2026

Explanation

• In a nuclear reactor, a moderator slows down fast neutrons.
• Slow (thermal) neutrons are more effective in sustaining fission.
• Moderators do not stop, absorb, or reflect neutrons completely.
• Common moderators are graphite and heavy water.

Last verified on 05-06-2026

Explanation

• Lyman series lies in the ultraviolet (UV) region of hydrogen spectrum.
• It is produced when an electron falls to the first energy level (n = 1).
• These transitions release high-energy photons.

Additional information:

• Balmer series lies in the visible region.
• Paschen and Brackett are in infrared.

Last verified on 05-06-2026

Explanation

• Photoelectric effect is the phenomenon where electrons are ejected from a metal surface.
• It occurs when light of suitable frequency falls on the metal.
• The incident photons transfer energy to electrons.
• If energy is sufficient, electrons are emitted from the surface.

Last verified on 05-06-2026

Explanation

• Entropy is a measure of disorder in a system.
• Increase in entropy means increase in randomness of particles.
• It also means energy becomes less available for useful work.

Last verified on 05-06-2026

Explanation

• Soap film shows brilliant colors due to interference of light.
• Light waves reflect from the top and bottom surfaces of the thin film.
• These reflected waves interfere with each other.
• Constructive and destructive interference produce different colors.

Last verified on 05-06-2026

Explanation

• In projectile motion, horizontal velocity has no acceleration.
• No force acts in the horizontal direction (ignoring air resistance).
• Therefore, horizontal velocity does not change with time.
• Only vertical velocity changes due to gravity.
• So, horizontal component remains constant.

Last verified on 05-06-2026

Explanation

Explanation

• Kinetic Molecular Theory (KMT) explains gas behavior using particle motion.
• It assumes gas molecules are in constant random motion.
• All collisions between gas molecules are perfectly elastic.
• Molecules do not have the same speed; speeds vary and depend on temperature.
• Therefore, “all molecules have same speed at different temperatures” is not a postulate.

Last verified on 05-06-2026

Explanation

For a grating, resolving power: R = mN

Where m = order of spectrum, N = total number of lines

1. Total lines N = width × lines per cm  

   N = 3 cm × 5000 lines/cm = 15,000 lines

2. Max resolving power happens at max order m.  

   For most basic problems, they take m = 3 as the highest practical order unless told otherwise.

So R_max = m × N = 3 × 15,000 = 45,000.

Last verified on 05-06-2026