Advertisements
Advertisements
प्रश्न
What are the two methods for obtaining coherent sources in the laboratory?
Advertisements
उत्तर
In the laboratory, coherent sources can be obtained by using (1) Lloyd's mirror and (2) Fresnel's biprism.
- Lloyd's mirror:
This is an extensively used device. The light from a source is made to fall at a grazing angle on a plane mirror as shown in figure.
Some of the light falls directly on the screen as shown by the blue lines in the figure and some light falls after reflection, as shown by the red lines. The reflected light appears to come from a virtual source and so we get two sources. They are derived from a single source and hence are coherent. They interfere and an interference pattern is obtained as shown in the figure. Note that even though we have shown the direct and reflected rays by blue and red lines, the light is monochromatic having a single wavelength. - Fresnel's biprism:
A biprism is a prism with a vertex angle of nearly 180°. It can be considered to be made up of two prisms with very small refracting angle ranging from 30′ to 1°, joined at their bases. In experimental arrangement, the refracting edge of the biprism is kept parallel to the length of the slit. Monochromatic light from a source is made to pass through a narrow slit S as shown in Figure and fall on the biprism.
The two halves of the biprism form virtual images S1 and S2. These are coherent sources having obtained from a single secondary source S. The two waves coming from S1 and S2 interfere and form interference fringes like that in Young’s double-slit experiment in the shaded region shown in the figure.
APPEARS IN
संबंधित प्रश्न
When a drop of oil is spread on a water surface, it displays beautiful colours in daylight because of ______________ .
The intensity at the central maximum (O) in a Young’s double slit experimental set-up shown in the figure is IO. If the distance OP equals one-third of the fringe width of the pattern, show that the intensity at point P, would equal `(I_0)/4`.
What are coherent sources of light?
Obtain the relation between phase difference and path difference.
What is a bandwidth of interference pattern?
Discuss the interference in thin films and obtain the equations for constructive and destructive interference for transmitted and reflected light.
The interference pattern is obtained with two coherent light sources of intensity ratio n. In the interference pattern, the ratio `("I"_"max" - "I"_"min")/("I"_"max" + "I"_"min")` will be ______
In Young's double slit experiment green light is incident on the two slits. The interference pattern is observed on a screen. Which one of the following changes would cause the observed fringes to be more closely spaced?
In Young's double-slit experiment, in an interference pattern, a second minimum is observed exactly in front of one slit. The distance between the two coherent sources is 'd' and the distance between source and screen is 'D'. The wavelength of the light source used is ______
A metal rod has length, cross-sectional area and Young's modulus as L, A and Y, respectively. If the elongation in the rod produced is l, then work done is proportional to ______.
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)
Two identical light waves having phase difference 'Φ' propagate in same direction. When they superpose, the intensity of the resultant wave is proportional to ______.
In Young's experiment, the distance between the slits is doubled and the distance between the slit and screen is reduced to half, then the fringe width ____________.
In a double slit experiment, the two slits are 2 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?
In a biprism experiment, D = 1 m, `lambda` = 6000 Å. When a convex lens is interposed between the biprism ru1d the eyepiece, then the distance between the images of the slits given by the Jens at two positions are 1.5 mm and 6.0 mm. The fringe width will be ______.
In Young's double slit experiment fifth dark fringe is formed opposite to one of the slits. If D is the distance between the slits and the screen and d is the separation between the slits, then the wavelength of light used is ______.
If the two slits in Young's double slit experiment have width ratio 9 : 1, the ratio of maximum to minimum intensity in the interference pattern is ______.
In a biprism experiment, the slit separation is 1 mm. Using monochromatic light of wavelength 5000 Å, an interference pattern is obtained on the screen. Where should the screen be moved? so that the change in fringe width is 12.5 x 105 m?
The graph shows the variation of fringe width (β) versus distance of the screen from the plane of the slits (D) in Young's double-slit experiment Keeping other parameters the same. The wavelength of light used can be calculated as d = distance between the slits ______
In a biprism experiment, monochromatic light of wavelength (λ) is used. The distance between two coherent sources is kept constant. If the distance between slit and eyepiece (D) is varied as D1, D2, D3, and D4, the corresponding measured fringe widths are z1, z2, z3, and z4 then ______
Two waves with same amplitude and frequency superpose at a point. The ratio of resultant intensities when they arrive in phase to that when they arrive 90° out of phase is ______.
`[cos pi/2=0]`
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)
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 ______.
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 ______.
The path difference between two interference light waves meeting at a point on the screen is `(87/2)lambda`. The band obtained at that point is ______.
In biprism experiment the maximum intensity is ‘I0’. If the path difference between the two interfering waves is ‘λ/4’ then intensity at the point on the screen is ______.
`[sin 45^circ = cos 45^circ = 1/sqrt 2]`
