Question
What are the dark lines seen in the solar spectrum called?
Solution
Fraunhoffer lines.
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Fraunhoffer lines.
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With the help of a labelled diagram, show that fringe separation β in Young’s double slit experiment is given by:
where the terms have their usual meaning.
Let S be a narrow slit luminated by monochromatic light, S1 and S2 be two parallel narrow slits very close to each other.
The light waves S reach S1 and S2 in some phase. According to Higgens principle S1 and S2 etc as new light sources from which secondary wavelet originate. These wavelet originate. These wavelets form interference fringes on screen.
Let a bright fringes be formed at P
Path difference. = (S2P - S1P)
ΔS2P - S1P = S2P - AP = S2A
(i) What is the difference between polarised light unpolarised light based on the direction of electric vector E?
(ii) What will be the effect on the width of the central bright fringe in the diffraction pattern of a single slit if :
(1) Monochromatic light of smaller wavelength is used.
(2) Slit is made narrower.
(i)
In unpolarised light the vibration of the electric vector E occur symmetrically in all possible directions in a plane perpendicular to direction of propagation of light in polarised light the vibration of electric vector E occur in a plane perpendicular to the direction of propagation of light and are confined to a single direction in the plane.
(ii)
1. Width will decrease
2. When slit is made narrower the central bright fringe becomes wider.
Biprism is made from a single glass plate by grinding and polishing so that it is a single prism with one of its angle 179° and the other two about 30’ each.
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