Video Lecture
Theory For Notes Making
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Objective Assignment
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Subjective Assignment
1.
(a)
State the importance of coherent sources in the phenomenon of interference.
(b)
In Young’s double slit experiment to produce interference pattern, obtain the conditions for constructive and destructive interference. Hence deduce the expression for the fringe width.
(c)
If the entire experimental apparatus of Young is immersed in water,how does the fringes width get affected?
2.
In Young’s double slit experiment, the two slits 0.15 mm apart are illuminated by monochromatic light of wavelength 450 nm. The screen is 1.0m away from the slits.
(a)
Find the distance of the second (i) bright figure, (ii) dark fringe from the central maximum.
(b)
How will the fringe pattern change if the screen is moved away from the slits ?
3.
In Young’s double slit experiment, what is the effect of following operations on interference fringes :
(i) The screen is moved away from the plane of the slits.
(ii) The monochromatic source is replaced by another monochromatic source of smaller wavelength.
(iii) The monochromatic source is replaced by a source of white light.
(iv) The width of the source slit is made wider.
(v) The separation between the two slits is increased.
(vi) The distance between the source slit and the plane of the two slits is increased.
(vii) The width of each of the two slits is of the order of wavelength of light source.
4.
The figure shows a ‘double slit experimental set-up, for observing interference fringes due to different component colours of white light. What would be the predominant colour of the fringes observed at the point.
(i) O, the central point.
(ii) P, where \displaystyle {{S}_{2}}P-{{S}_{1}}P=\frac{{{{\lambda }_{b}}}}{2}? (here \displaystyle {{\lambda }_{b}}is the wavelength of the blue colour).
5.
Two slits are made one millimetre apart and the screen is placed one meter away. What is the fringe separation when blue-green light of wavelength 500nm is used ?
6.
In Young’s double-slit experiment using monochromatic light of wavelength \displaystyle \lambda , the intensity of light at a point on the screen where path difference is \displaystyle \lambda , is K units. What is the intensity of light at a point where path difference is \displaystyle \lambda /3?
7.
In double-slit experiment using light of wavelength 600 nm, the angular width of a fringe formed on a distant screen is 0.1º. What is the spacing between the two slits?
8.
Mark the statement true or false :
(a) In Young’s double slit experiment, performed with a source of white light, only black and white fringes are observed.
(b) Two slits in Young’s double slit experiment are illuminated by two different sodium lamps emitting light of same wavelength. No interference pattern will be obtained.
9.
In Young’s double slit experiment, monochromatic light of wavelength 630 nm illuminates the pair of slits and produces an interference pattern in which two consecutive bright fringes are separated by 8.1 mm. Another source of monochromatic light produces the interference pattern in which the two consecutive bright fringes are separated by 7.2 mm. Find the wavelength of light from the second source. What is the effect on the interference fringes if the monochromatic source is replaced by a source of white light ?
10.
In a Young’s experiments, the width of the frings obtained with light of wavelength 6000 Ǻ is 2.0 mm. What will be the fringe width, if the entire apparatus is immersed in a liquid of refractive index 1.33 ?
11.
A beam of light, consisting of two wavelengths, 600 nm and 450 nm is used to obtain interference fringes in a Young’s double slit experiment. Find the least distance, from the central maximum, where the bright fringes, due to both the wavelengths, coincide. The distance between the two slits is 4.0 mm and the screen is at a distance 1.0 m from the slits.
12.
In a Young’s double-slit experiment, the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in the experiment.
13.
A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in a Young’s double-slit experiment.
(a) Find the distance of the third bright fringe on the screen from the central maximum for wavelength 650 nm.
(b) What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide?
14.
In a double-slit experiment the angular width of a fringe is found to be 0.2° on a screen placed 1 m away. The wavelength of light used is 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water? Take refractive index of water to be 4/3.
15.
In a Young’s double slit experiment,
(a) deduce the conditions for constructive and destructive interference. Hence write the expression for the distance between two consecutive bright or dark fringes.
(b) \displaystyle {{S}_{1}} and \displaystyle {{S}_{2}}
(c) Plot a graph of the intensity distribution vs path difference in this experiment. Compare this with the intensity distribution of fringes due to diffraction at a single slit. What important difference do you observe ?
16.
In a Young’s double slit experiment, the two slits are kept 2mm apart and the screen is positioned 140 cm away from the plane of the slits. The slits are illuminated with light of wavelength 600 nm. Find the distance of the third bright fringes, from the central maximum, in the interference pattern obtained on the screen. If the wavelength of the incident light were changed to 480 nm, find out the shift in the position of third bright fringe from the central maximum.
17.
Find the ratio of intensities at two points on a screen in Young’s double slit experiment, when waves from two slits have path difference of (i) 0 and (ii) \displaystyle \lambda /4.
18.
In YDSE, the width of the fringes obtained with light of wavelength 6000 Å is 2mm. Calculate the fringe width if the entire apparatus is immersed in a liquid medium of refractive index 1.33.
19.
The two slits of Young’s double slit experiment are separated by a distance of 0.03 mm. When light of wavelength 5000 Å falls on the slits, an interference pattern is produced on the screen 1.5 m away. Find the distance of fourth bright fringe from the central maximum.