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The Photon Model of Light
Electromagnetic radiation can be described using a photon model.
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The Photon Model of Light
Light can be thought of as arriving in tiny packets of energy called photons.
Higher-frequency light has more energetic photons.
Recommended for Class 10
The Photon Model of Light
Electromagnetic radiation can be described using a photon model.
A photon is a quantum of electromagnetic radiation.
The energy of a photon is:
**E = hf**
where:
`E` = photon energy `h` = Planck's constant `f` = frequency
Frequency and Energy
Higher frequency means greater photon energy.
Therefore:
Gamma-ray photons have much more energy than radio-wave photons.
Photon Momentum
Photons also carry momentum:
**p = hλ**
where:
`p` = photon momentum `λ` = wavelength
Wave-Particle Idea
Electromagnetic radiation shows both wave-like and particle-like behaviour.
The wave model explains phenomena such as diffraction and interference.
The photon model is useful for explaining energy transfer in interactions with matter.
The Photon Model of Light — Advanced
The photon model quantizes electromagnetic energy and momentum. Individual photon energy depends only on frequency, while beam intensity depends on photon flux and photon energy together.
Common Mistakes
Common Mistakes
- Mistake
A photon is not a tiny classical ball of light.
- Mistake
Photon energy depends on frequency, not brightness alone.
- Mistake
A brighter beam usually means more photons per unit time and/or greater total energy flow, not necessarily more energy per photon.
Revision Zone
60-Second Revision
Quick cues from this topic — use them for last-minute revision.
Photon → quantum of EM radiation.
**E=hf**
Higher frequency → higher photon energy.
- Definition
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Practice
PQ
Q1. Define photon.
PQ
Q2. Write E=hf.
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Q3. Explain frequency-energy relation.
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Q4. Write p=hλ.
PQ
Q5. Distinguish brightness and photon energy.
Exam Practice
EQ
Q1. Define photon.
EQ
Q2. State photon energy equation.
EQ
Q3. Explain why gamma photons are more energetic than radio photons.
EQ
Q4. State photon momentum equation.
EQ
Q5. Explain wave-particle behaviour briefly.
School-standard facts for Matric and Intermediate. Original explanations — not copied from textbooks.