The buoyant force on an object immersed in a fluid depends on MCQ with Answer and Explanation

Explanation:
Photoelectric effect requires photon energy hν ≥ work function φ of metal. Thus frequency ν must exceed threshold ν₀ = φ/h, regardless of intensity. Intensity affects number of electrons, not emission possibility. Memory aid: 'Photoelectric: frequency threshold (quantum effect); intensity affects current, not emission'. This quantum physics concept is frequently tested in competitive exams. Always distinguish classical wave prediction (intensity-dependent) from quantum reality (frequency-dependent); this was key evidence for photons.

Explanation:
Leading zeros not significant. '450' has three digits, but the trailing zero after decimal is significant (4,5,0). So 3 significant figures. 0.00450 is 3 SF.

Explanation:
Assertion is true: in resistive AC circuits, V and I reach peaks simultaneously (phase difference 0°). Reason is true and explains A: resistors obey Ohm's law instantaneously (V=IR), with no energy storage mechanism (unlike capacitors/inductors that cause phase shifts via energy storage/release). Thus, no phase difference arises. Memory aid: 'Resistors: V and I in phase; Capacitors: I leads V; Inductors: V leads I'. This assertion-reason question tests AC circuit fundamentals, frequently examined. Always link phase behavior to energy storage properties of components.