Torque τ = r×F: [L][MLT⁻²] = [ML²T⁻²]. Work W = F·d: same dimensions. Physically distinct: torque (vector, rotational), work (scalar, energy). Memory tip: 'Torque and work: same [ML²T⁻²]; different physical meaning'. Dimensional analysis frequently tested in competitive exams.
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.
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