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प्रश्न
What are the conditions for obtaining a good interference pattern? Give reasons.
What is the essential condition for obtaining sustained interference?
उत्तर १
The conditions necessary for obtaining a well-defined and steady interference pattern are:
- The two sources of light should be coherent: This is the essential condition for getting a sustained interference pattern. As we have seen, the waves emitted by two coherent sources are always in phase or have a constant phase difference between them at all times. If the phases and phase differences vary with time, the positions of maxima and minima will also change with time, and the interference pattern will not be steady. For this reason, it is preferred that the two secondary sources used in the interference experiment are derived from a single original source.
- The light should be monochromatic: As can be seen from the condition of bright and dark fringes, the position of these fringes as well as the width of the fringes depend on the wavelength of light and the fringes of different colours are not coincident. The resultant pattern contains coloured, overlapping bands.
- The two interfering waves must have the same amplitude: Only if the amplitudes are equal, the intensity of dark fringes (destructive interference) is zero and the contrast between bright and dark fringes will be maximum.
- The two light sources should be narrow: If the slits are broad, the distances from different points along the slit to a given point on the screen are significantly different and therefore, the waves coming through the same slit will interfere among themselves, causing blurring of the interference pattern.
- The interfering light waves should be in the same state of polarization: Otherwise, the points where the waves meet in the opposite phase will not be completely dark and the interference pattern will not be distinct.
- The two waves should be in the same state of polarization: This is necessary only if polarized light is used for the experiment.
उत्तर २
- The two light sources must be coherent, which implies that the light waves they emit must have a constant phase difference or be the same phase.
- The two series must emit light of the same wavelength, but the amplitude between them should differ as little as possible.
संबंधित प्रश्न
Write the necessary conditions to obtain sustained interference fringes.
A long narrow horizontal slit is paced 1 mm above a horizontal plane mirror. The interference between the light coming directly from the slit and that after reflection is seen on a screen 1.0 m away from the slit. Find the fringe-width if the light used has a wavelength of 700 nm.
Answer in brief:
In Young's double-slit experiment what will we observe on the screen when white light is incident on the slits but one slit is covered with a red filter and the other with a violet filter? Give reasons for your answer.
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Two coherent sources whose intensity ratio is 25:1 produce interference fringes. Calculate the ratio of amplitudes of light waves coming from them.
How does wavefront division provide coherent sources?
What is a bandwidth of interference pattern?
Does diffraction take place at Young’s double-slit?
In Young’s double slit experiment, the slits are 2 mm apart and are illuminated with a mixture of two wavelength λ0 = 750 nm and λ = 900 nm. What is the minimum distance from the common central bright fringe on a screen 2 m from the slits where a bright fringe from one interference pattern coincides with a bright fringe from the other?
The light waves from two independent monochromatic light sources are given by, y1 = 2 sin ωt and y2 = 3 cos ωt. Then the correct statement is ____________.
On a rainy day, a small oil film on water shows brilliant colours. This is due to ____________.
The distance between the first and ninth bright fringes formed in a biprism experiment is ______.
(`lambda` = 6000 A, D = 1.0 m, d = 1.2 mm)
A wire of length 'L' and area of cross-section · A' is made of material of Young's modulus 'Y'. It is stretched by an amount 'x'. The work done in stretching the wire is ______.
In Young's experiment for the interference of light, the separation between the silts is d and the distance of the screen from the slits is D. If D is increased by 0.6% and d is decreased by 0.2%, then for the light of a given wavelength, which one of the following is true?
"The fringe width ____________."
A thin mica sheet of thickness 4 x 10-6 m and refractive index 1.5 is introduced in the path of the first wave. The wavelength of the wave used is 5000 A. The central bright maximum will shift ______.
In a Young's experiment, two coherent sources are placed 0.60 mm apart and the fringes are observed one metre away. If it produces the second dark fringe at a distance of 1 mm from the central fringe, the wavelength of monochromatic light used would be ____________.
In Young's double slit experiment with a source of light of wavelength 5860 Å, the first maxima will occur when ____________.
In Young's double slit experiment the source is white light. One slit is covered with red filter and the other with blue filter. There shall be ____________.
The phenomenon of interference is based on ______.
Two coherent light sources of intensity ratio 'n' are employed in an interference experiment. The ratio of the intensities of the maxima and minima in the interference pattern is (I1 > I2).
In biprism experiment, the 4th dark band is formed opposite to one of the slits. The wavelength of light used is ______.
In a double slit experiment, the separation between the slits is d and distance of screen from slits is D. If the wavelength of light used is `lambda` and I is the intensity of central bright fringe, then intensity at distance x from central maximum is given by ____________.
Young's double slit experiment is performed in water, instead of air, then fringe width ______.
A double slit experiment is immersed in water of refractive index 1.33. The slit separation is 1 mm, distance between slit and screen is 1.33 m. The slits are illuminated by a light of wavelength 6300 Å. The fringe width is ______.
In Young's double-slit experiment, the distance between the slits is 3 mm and the slits are 2 m away from the screen. Two interference patterns can be obtained on the screen due to light of wavelength 480 nm and 600 run respectively. The separation on the screen between the 5th order bright fringes on the two interference patterns is ______
In an interference experiment, the intensity at a point is `(1/4)^"th"` of the maximum intensity. The angular position of this point is at ____________.
(cos 60° = 0.5, `lambda` = wavelength of light, d = slit width)
Two coherent sources of intensities I1 and I2 produce an interference pattern on the screen. The maximum intensity in the interference pattern is ______
If we have two coherent sources S1 and S2 vibrating in phase, then for an arbitrary point P constructive interference is observed whenever the path difference is ______.
What is meant by Constructive interference?
A beam of electrons is used in Young's double-slit experiment. If the speed of electrons is increased then the fringe width will ______.
How will the interference pattern of Young's double slit change if one of the two slits is covered by a paper which transmits only half of the light intensity?
The interference pattern is obtained with two coherent light sources of intensity ratio 4 : 1. And the ratio `("I"_"max" - "I"_"min")/("I"_"max" + "I"_"min")` is `5/x`. Then the value of x will be equal to ______.
Interference fringes are produced on a screen by using two light sources of intensities I and 9I. The phase difference between the beams is `pi/2` at point P and π at point Q on the screen. The difference between the resultant intensities at point P and Q is ______.
