Which of the following is not a fundamental unit in SI? MCQ with Answer and Explanation

Explanation:
During beta decay, a neutron in an unstable nucleus transforms into a proton and an electron. The proton remains in the nucleus, but the electron is ejected at high speed. These ejected, high-energy electrons are called beta rays (or beta particles). Gamma rays are electromagnetic waves, and alpha particles are helium nuclei.

Explanation:
Moderator slows fast neutrons to thermal energies to increase probability of fission. Common moderators: heavy water, graphite. Control rods (cadmium, boron) absorb neutrons. Coolant removes heat.

Explanation:
Dispersion (splitting of white light into colors) occurs because refractive index n varies with wavelength (Cauchy's relation: n ∝ 1/λ² approximately). Since v = c/n, different colors travel at different speeds in the medium, causing different refraction angles (Snell's law). Frequency remains constant across media. Memory tip: 'Dispersion: n(λ) ⇒ v(λ) ⇒ different bending; violet bends most (highest n)'. This optics concept is frequently tested in competitive exams. Always distinguish cause (speed variation) from property (frequency/wavelength); competitive exams often test this nuanced understanding.