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(a) Define a wavefront. Using Huygen's principle, verify the laws of reflection at a plane surface. (b) In a single-slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band? Explain. (c) When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the obstacle. explain why. |
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Answer» Solution :(b) When slit width .a. is doubled, angular width (and, consequently, the linear width too) of central diffraction band GIVEN by `theta=pm(LAMDA)/(a)` is reduced to one-half of its previous value. Consequently, the amplitude of light for central diffraction band will become twice of its previous value and as a result, the new intensity will be 4 times the origiinal value. (c) Waves diffraction from the edge of the CIRCULAR OBSTACLE INTERFERE constructively at the centre of the shadow of circular obstacle. as a result, the centre point is a bright spot. |
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