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:
Ohm's law applies to ohmic materials (metals) at constant temperature. Non-ohmic devices (diodes, filaments) have nonlinear V-I characteristics. Memory tip: 'Ohmic = linear V-I graph through origin; temperature must be constant'. Conceptual question testing Ohm's law limitations, frequently examined in competitive exams.
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