Question

Does the principle of conservation of energy hold for interference and diffraction phenomena? Explain briefly.

Answer 1

Hint: During interference of light, all the bright fringes formed have maximum and equal intensity and all dark fringes formed have minimum intensity and are completely dark.
During diffraction of light, the bright fringes do not have equal intensity and dark fringes in spite of being completely dark, have less bright fringes as compared to the bright fringes.

Complete step by step answer:
Conservation of energy basically means that the energy can never be created nor be destroyed.
Let us first discuss the case of interference.
During interference of light, all the bright fringes formed have maximum and equal intensity and all dark fringes formed have minimum intensity and are completely dark. It means the energy is equally distributed among the bright and the dark fringes which implies energy is conserved in case of interference of light.
Now, let us discuss the case of diffraction.
During diffraction of light, the bright fringes do not have equal intensity and dark fringes in spite of being completely dark, have less bright fringes as compared to the bright fringes. But the energy is simply redistributed among the bright and dark fringes which also implies that the energy is conserved.
Hence, in both the cases, interference and diffraction, conservation of energy takes place.

Note: Interference of light occurs when any two coherent light waves of same frequency are simultaneously present at a point while diffraction is the bending of light waves around the corners of an obstacle or aperture. Diffraction is of two classes, Fresnel and Fraunhofer.