Question

Dual nature of radiation is shown by:
(A). Diffraction and reflection.
(B). Refraction and diffraction.
(C). Photoelectric effect alone.
(D). Photoelectric effect and diffraction.

Answer 1

Hint: Radiations are electromagnetic waves that do not require a medium for its propagation. White light, that is visible to us, is the best example of such radiations. The radiation from the Sun reaches our Earth via space, that is, it does not require a medium. Many experiments were conducted on these radiations to study its nature. Radiations show both particle and wave nature and hence have a dual nature.

Complete step by step answer:
Diffraction is the property of radiation to bend when it passes through an aperture or an edge. The bending is possible only if the radiation has a wave nature. Reflection and refraction show that radiation beams or rays change their direction when incident on a reflective surface or when incident on an optically denser medium. It does not explain the particle nature of the radiations. The photoelectric effect of radiation says that when a photon of radiation hits a metal surface if the energy of the photos is more than the threshold energy of the metal, it causes the emission of electrons. This effect depicts radiations as a packet of energy or a particle having one phonon energy. Hence the properties of photoelectric effect and diffraction explain the dual nature of radiation.
Therefore, the correct option is D.

Additional information:
Optically denser medium need not be physically denser. The electromagnetic spectrum gives the range of electromagnetic radiations arranged according to their frequencies. It starts from the radio waves and extends to the gamma rays. All the regions of the electromagnetic spectrum are light. But only some regions are only visible to us. The threshold energy is the minimum energy below which the emission of electrons does not take place completely from a metal surface.

Note: The refraction and reflection show the wave nature of radiation. But most of them will think that it is due to the particle nature of light. That is a misconception. It is better to remember the experiments like double-slit experiment and black body concepts done by the scientists to prove the dual nature of photons.
Petrol is optically denser than water even though it is physically lighter than water.