question_answer

Two narrow slits are illuminated by a single monochromatic source. Name the pattern obtained on the screen. One of the slits is now completely covered. What is the name of the pattern now obtained on the screen? Draw intensity pattern obtained in the two cases. Also write two differences between the patterns obtained in the above two cases.

Answer:

                                                       With two narrow slits, an interference pattern is obtained. When one slit is completely covered, diffraction pattern is obtained. For intensity distribution curve for interference, see Fig. For intensity distribution curve for diffraction, see Fig.

Interference	Diffraction
Fringes are of equal width	Fringes are of unequal width
Fringes are of equal intensity	Fringes are of decreasing intensity
Due to superposition of two different wave fronts	Due to superposition of secondary wavelets from different parts of the same wave front
Maxima occur at \[\theta =\frac{\lambda }{a}\]	Minima occur at \[\theta =\frac{\lambda }{a}\]