question_answer

State the condition for diffraction of light to occur. In the diffraction at a single slit experiment, how would the width and the intensity of central maximum change, if (i) slit width is halved and (ii) visible light of longer wavelength is used?

Answer:

                Diffraction of light is highly pronounced if the size of the obstacle or aperture is comp-arable to the wavelength of the light used. Width of central maximum \[=\frac{2D\lambda }{d}\] (i) If slit width d is halved, width of central maximum is doubled. Its area becomes 4 times and hence intensity becomes one-fourth of the initial intensity. (ii) If visible light of longer wavelength is used, width of central maximum increases and hence intensity decreases.