The defect of vision in which the lens becomes opaque is called MCQ with Answer and Explanation

Explanation:
When a wave (like light or sound) changes mediums, its velocity changes due to the new medium's optical or mechanical density. Wavelength changes proportionally with velocity (v = fλ). However, frequency is determined solely by the source generating the wave and the energy of the photons/particles, and it remains absolutely constant.

Explanation:
Alpha (α) radiation: helium nucleus (²He⁴, 2p+2n), +2 charge, low penetration. Beta: electrons; Gamma: photons; Neutron: neutral particle. Memory aid: 'Alpha = He nucleus; Beta = electron; Gamma = EM wave'. Radioactivity classification frequently tested in competitive exams to distinguish radiation types.

Explanation:
Mercury used due to uniform expansion, visibility, high boiling point.