The mechanical advantage of a lever is given by MCQ with Answer and Explanation

Explanation:
Laws of reflection: (1) Angle of incidence (i) equals angle of reflection (r); (2) Incident ray, reflected ray, and normal at point of incidence all lie in the same plane. Option D describes refraction, not reflection. These laws hold for all reflecting surfaces (plane, curved). Memory tip: 'i = r and coplanar rays'. This definition-based question tests precise recall of fundamental optics laws, frequently examined in competitive exams. Always distinguish reflection laws (i=r) from refraction laws (Snell's law: n₁sin i = n₂sin r).

Explanation:
λ = h/(mv) = 6.63×10⁻³⁴/(1×10) = 6.63×10⁻³⁵ m. Extremely small, not observable. For electron it's significant. de Broglie hypothesis: matter waves. This is modern physics.

Explanation:
g = GM/R² = G (ρ 4/3 π R³)/R² ∝ ρ R. If radius half, density same, g becomes half. Weight half = 50 N.