Chemistry · Structure Of Atom · NEET
No. This is the most common confusion. In any single experiment, light shows only ONE nature. When light travels through space (interference, diffraction), it acts as a wave. When light strikes matter and gives up energy (photoelectric effect, black body radiation), it acts as particles (photons). Both natures are true, but they never appear together in the same experiment. NCERT says clearly: 'Depending on the experiment, we find that light behaves either as a wave or as a stream of particles.'
Interference and diffraction. These are wave-only behaviours. A wave can bend around edges (diffraction) and two waves can add up or cancel out (interference). Particles cannot do this. So any question that mentions interference or diffraction is pointing to the WAVE nature. This wave nature also explains why light has a wavelength and frequency.
The photoelectric effect and black body radiation. In the photoelectric effect, light knocks electrons out of a metal instantly, one photon hitting one electron, like a ball hitting a ball. Wave theory could not explain this. Planck's black body radiation also needed light energy to come in packets (quanta). So both of these prove light is made of particles called photons, each carrying energy E = h times nu.
A photon is one small packet (quantum) of light energy. Its energy is E = h times nu, where h is Planck's constant (6.626 x 10^-34 J s) and nu is the frequency. A brighter light does not mean bigger photons; it means MORE photons. The energy of each photon depends only on frequency, not on brightness. This is the particle picture of light.
Because one picture alone fails. The wave picture explains interference and diffraction but CANNOT explain the photoelectric effect. The particle picture explains the photoelectric effect and black body radiation but CANNOT explain interference or diffraction. Since each picture explains half the facts, scientists accepted that light has both natures. NCERT calls this a 'dilemma' that was solved only by accepting dual behaviour.
Yes. Later, de Broglie showed that matter particles such as electrons also show wave-particle duality. Every moving particle has a wavelength, lambda = h / (m v). This is a separate concept (de Broglie wavelength), but the idea started here: if light (a wave) can act like a particle, then a particle can also act like a wave.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Light behaves as a wave when it travels (interference, diffraction) and as particles called photons when it interacts with matter (photoelectric effect).
Max Planck introduced energy quanta (E = h nu) in 1900, and Einstein in 1905 used this to explain the photoelectric effect, treating light as a stream of photons.
Interference and diffraction. These behaviours can only be explained if light is a wave. Particles cannot interfere or diffract.
The photoelectric effect and black body radiation. Both need light energy to come in fixed packets (photons), which wave theory could not explain.
No. de Broglie showed that moving particles like electrons also have a wave nature, with wavelength lambda = h / mv. So matter also shows wave-particle duality.
It links black body radiation, the photoelectric effect, and de Broglie waves. NEET often tests which experiment shows which nature, and traps students with the word 'simultaneously'.
