The least count of a standard vernier calliper is generally MCQ with Answer and Explanation

Explanation:
Myopia (nearsightedness) requires diverging lens (concave). Hypermetropia needs convex.

Explanation:
p = mv ⇒ λ = h/(mv) ⇒ λ ∝ 1/v for constant mass. Higher velocity ⇒ shorter wavelength. Memory tip: 'λ = h/mv; faster particle ⇒ smaller wavelength'. Quantum mechanics relation frequently tested in competitive modern physics sections.

Explanation:
Proton mass ≈ 1.67 × 10⁻²⁷ kg, electron ≈ 9.11 × 10⁻³¹ kg, ratio ≈ 1836. Neutron slightly heavier. Atomic mass concentrated in nucleus.