Question: Q. 1. Figure shows a standard two-slit arrangement with slits $S_{1}, S_{2} . P_{1}, P_{2}$ are the two minima points on either side of $P$ shows in Figure. At $P_{2}$ on the screen, there is a hole and behind $P_{2}$ is a second screen, 2-slit arrangement with slits $S_{3}$ and $S_{4}$ and a second screen behind them.
(a) There would be no interference pattern on the second screen but it would be lighted. (b) The second screen would be totally dark.
(c) There would be a single bright point on the second screen.
(d) There would be a regular two slit pattern on the second screen.
[NCERT Exemplar]
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Solution:
Ans. Correct options : (d)
Explanation: As $P_{2}$ is minima due to two wave fronts in opposite phase coming from, two slits $S_{1}$ and $S_{2}$, but there is wavefronts from $S_{1}, S_{2}$. So $P_{2}$ will act as a source of secondary wavelets. Wavefront starting from $P_{2}$ reaches at $S_{3}$ and $S_{4}$ slits which will again act as two monochromatic or coherent sources and will form pattern on second screen.
Very Short Answer Type Questions
[AI Q. 1. Name the phenomenon which proves transverse wave nature of light. Give two uses of the devices whose functioning is based on this phenomenon.
R [SQP 2014]
Ans. Polarisation,
Two uses : Polaroids can be used in sunglasses, window panes, photographic cameras and 3D movie cameras.
(Any two) $1 / 2+1 / 2$
[CBSE Marking Scheme 2014]
