Particle Nature Of Light
A sensitive detector registers dim starlight arriving as discrete individual clicks rather than a smooth continuous signal, and an astronomer interprets this observation.
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About This Question
- Subject
- physics
- Chapter
- dual nature of matter and radiation
- Topic
- particle nature of light
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Light energy is delivered in discrete quanta called photons
NCERT explains that light exhibits a particle nature whereby its energy is not spread continuously but arrives in indivisible packets called photons, each of energy hν. When a source is extremely faint, so few photons arrive that a sensitive detector can register each one separately, producing discrete clicks rather than a steady signal. This granular arrival is direct evidence for the quantum, particle-like character of light, complementing its wave behaviour in interference. The option blaming detector malfunction is wrong because the discrete clicks are a genuine and reproducible physical phenomenon, not an artefact. The option about waves vanishing and reappearing is wrong because light does not disappear in transit; rather its energy is inherently quantized. The option about dust blocking the beam is wrong because random obstruction would dim the signal irregularly, not reveal the fundamental one-by-one photon arrival. As stated in NCERT Class 12, Chapter 11, the photoelectric effect and photon detection together confirm the particle nature of radiation. A consistency check confirms that discrete detection events are exactly what a photon picture predicts for very low light levels.
This easy difficulty physics question is from the chapter dual nature of matter and radiation, covering the topic of particle nature of light. It appeared in the 2025 exam.
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