Dual Nature of Matter and Radiation – JEE Mains Physics

• by Zenith LMS
• Updated April 2025

1. Dual Nature of Radiation

• The dual nature of radiation refers to the fact that light exhibits both wave-like and particle-like properties. In some experiments, light behaves as a wave, while in others, it behaves as a stream of particles called photons.

2. Photoelectric Effect

• The photoelectric effect occurs when light strikes a material and causes the emission of electrons from the material's surface. The intensity and frequency of light affect the number and energy of emitted electrons.

3. Hertz and Lenard's Observations

• Hertz observed that ultraviolet light causes sparks to jump between two electrodes, confirming the particle nature of light. Lenard’s experiments showed that the emission of photoelectrons did not depend on the intensity of light but on its frequency.

4. Einstein's Photoelectric Equation

• Einstein explained the photoelectric effect by proposing that light is made up of photons, and the energy of these photons is related to their frequency by the equation:

E = hν

• Where E is the energy of the photon, h is Planck’s constant, and ν is the frequency of the light. This equation helped establish the particle nature of light.

5. Particle Nature of Light

• The particle nature of light is evident in phenomena like the photoelectric effect, Compton scattering, and the discrete energy levels in atoms. Light behaves as a stream of particles called photons, which have energy and momentum.

6. Matter Waves: Wave Nature of Particles

• According to de Broglie, all matter has wave-like properties. He proposed that particles like electrons have an associated wavelength (matter waves), which is given by the relation:

λ = h/p

• Where λ is the wavelength, h is Planck's constant, and p is the momentum of the particle.

7. de Broglie Relation

• de Broglie’s relation connects the wave nature of particles with their momentum. The wavelength (λ) associated with a particle is inversely proportional to its momentum, showing that smaller particles (like electrons) have noticeable wave-like properties.