wave-optics Question 13
Question: Q. 4. How does the angular separation between fringes in single-slit diffraction experiment change when the distance of separation between the slit and screen is doubled?
[O.D. I, II, III, 2012]
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Solution:
Ans. No change. [CBSE Marking Scheme 2012] 1
Short Answer Type Questions-I
[II Q. 1. Draw the intensity pattern for single slit diffraction and double slit interference. Hence, state two differences between interference and diffraction patterns.
U] [OD, Foreign 2017]
Differences :
| Interference | Diffraction |
|---|---|
| All maxima have equal intensity |
 |
| All fringes have equal width |
Different (changing) width |
| Superposition of two wavefronts |
Superposition of wavelets from the same wavefront |
(Any two)
[CBSE Marking Scheme 2017]
Commonly Made Error
- (i) Some students do not know the correct difference between interference of light and diffraction of light.
Detailed Answer :
Intensity Pattern :
Inteference fringe pattern Diffraction fringe pattern
$$ 1 / 2+1 / 2 $$
Difference between Interference and Diffraction :
| Interference | Diffraction |
|---|---|
| Fringe width is constant. | Fringe width varies. |
| Fringes are obtained with the coherent light coming from two slits. |
Fringes are obtained with the monochromatic light coming from single slit. |
| It is superposition of waves. |
It superposition of many waves. |
| It depends upon the distance between two openings. |
It depends upon the aperture of single slit opening. |
| Many fringes are visible. | Fewer fringes are visible. |
| All fringes are of same brightness. |
Central fringe has maximum brightness, then it reduces gradually. |
(Any two) $1 / 2+1 / 2$
