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

Explanation

• A vector field with zero curl is called an irrotational field.
• Curl measures the tendency of rotation in a vector field.
• If curl = 0, there is no local rotation present.
• Such fields are derived from a scalar potential.

Last verified on 05-06-2026

Explanation

• The reciprocal lattice of a body-centered cubic (BCC) lattice is face-centered cubic (FCC).
• In crystallography, direct and reciprocal lattices are inversely related.
• FCC ↔ BCC are reciprocal to each other.
• Simple cubic (SC) is self-reciprocal.

Last verified on 05-06-2026

Explanation

• Einstein’s photoelectric equation explains energy conservation in photoelectric effect.
• Incident photon energy is used to overcome work function.
• Remaining energy becomes kinetic energy of emitted electron.
• Therefore, correct equation is hv = hv₀ + (1/2 mv²)max.
• Photoelectric effect was explained by Albert Einstein (1905).

Last verified on 05-06-2026

Explanation

• In gamma (γ) decay, only energy is released from the nucleus.
• The atomic number (Z) and mass number (A) do not change.
• The nucleus before and after decay remains the same element.
• Here, the product nucleus is Ni⁶⁵₂₈, so the parent nucleus is also Ni⁶⁵₂₈.

Last verified on 05-06-2026

Explanation

• Increasing the number of slits in a diffraction grating increases intensity.
• More slits means more waves interfere constructively at the central maximum.
• This results in stronger and sharper central bright fringe.
• Energy is concentrated more effectively in the main maxima.

Last verified on 05-06-2026

Explanation

• Driven harmonic oscillator is a system undergoing forced vibration.
• In forced vibrations, an external periodic force continuously acts on the system.
• The system oscillates with the frequency of the applied force.
• This differs from free oscillations, where no external force acts.

Last verified on 05-06-2026

Explanation

• He–Ne laser is a four-level laser system.
• It uses a mixture of helium and neon gases as the active medium.
• Four-level lasers are more efficient because population inversion is easier to achieve.
• Ruby laser is a three-level laser.

Last verified on 05-06-2026