CBSE Class 12th Physics Chapter 10 - Wave Optics Important Questions with Answers
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Draw the intensity pattern for single slit diffraction and double slit interference. Hence, state two differences between interference and diffraction patterns. (All India 2017)
Question 2.
Unpolarised light is passed through a polaroid P1 When this polarised beam passes through another polaroid P2 and if the pass axis of P2 makes angle 6 with the pass axis of P1, then write the expression for the polarised beam passing through P2. Draw a plot showing the variation of intensity when ? varies from 0 to 2?. (All India 2017)
Question 3.
Why does Sun appear red at sunrise and sunset? (All India 2016)
Question 4.
A beam of unpolarised light is incident, on the boundary between two transparent media, at an angle of incidence = iB, the Brewester’s angle. At what angle does the reflected light get polarised? (Comptt. All India 2016)
Question 5.
Distinguish between unpolarised and a linearly polarised light. Describe, with the help of a diagram, how unpolarised light gets linearly polarised by scattering. (Comptt. Delhi 2016)
Question 6.
State Brewster’s law. The value of Brewster angle for a transparent medium is different for light of different colours. Give reason. (Delhi 2016)
Question 7.
(i) In Young’s double slit experiment, deduce the condition for
(a) constructive,’ and
(b) destructive interference at a point on the screen. Draw a graph showing variation of intensity in the interference pattern against position ‘x’ on the screen.
(ii) Compare the interference pattern observed in Young’s double slit experiment with single slit diffraction pattern, pointing out three distinguishing features. (Delhi 2016)
Question 8.
(a) Draw a diagram showing the ‘Young’s arrangement’ for producing ‘a sustained interference pattern’. Hence obtain the expression for the width of the interference fringes obtained in this pattern.
(b) If the principal source point S were to be moved a little upwards, towards the slit S1 from its usual symmetrical position, with respect to the two slits S1 and S2, discuss how the interference pattern, obtained on the screen, would get affected. (Compt. Delhi 2016)
Question 9.
Based on Huygen’s construction, draw the shape of a plane wavefront as it gets refracted on passing through a convex lens. (Comptt. All India 2016)
Question 10.
When a plane wave front, of light, of wavelength X, is incident on a narrow slit, an intensity distribution pattern, of the form shown is observed on a screen, suitably kept behind the slit. Name the phenomenon observed.
(a) Obtain the conditions for the formation of central maximum and secondary maxima and the minima.
(b) Why is there significant fall in intensity of the secondary maxima compared to the central maximum, where as in double slit experiment all the bright fringes are of the same intensity?
(c) When the width of the slit is made double the original width, how is the size of the central band affected? (Comptt. All India 2016)
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Question 1.
(a) Distinguish between unpolarised light and linearly polarised light. How does one get linearly polarised light with the help of a Polaroid?
(b) A narrow beam of unpolarised light of intensity I0 is incident on a polaroid P1. The light transmitted by it is then incident on a second polaroid P2 with its pass axis making angle of 60° relative to the pass axis of P1. Find the intensity of the light transmitted by P2. (Delhi 2016)
Question 2.
(a) Explain two features to distinguish between the interference pattern in Young’s double slit experiment with the diffraction pattern obtained due to a single slit.
(b) A monochromatic light of wavelength 500 nm is incident normally on a single slit of width 0.2 mm to produce a diffraction pattern. Find the angular width of the central maximum obtained on the screen.
Estimate the number of fringes obtained in Young’s double slit experiment with fringe width 0.5 mm, which can be accommodated within the region of total angular spread of the central maximum due to single slit. (Delhi. 2016)
Question 3.
(a) Define wavefront. Use Huygens’ principle to verify the laws of refraction.
(b) How is linearly polarised light obtained by the process of scattering of light? Find the Brewster angle for air—glass interface, when the refractive index of glass = 1.5. (All India 2016)
Question 4.
Explain with diagram, how plane polarized light can be produced by scattering of sunlight. An incident beam of light of intensity IG is made to fall on a polaroid A. Another polaroid B is so oriented with respect to A that there is no light emerging out of B. A third polaroid C is now introduced mid-way between A and B and is so oriented that its axis bisects the angle between the axes of A and B. Calculate the intensity of light transmitted by A, B and C. (Comptt. Delhi 2016)
Question 5.
(a) In Young’s double slit experiment a monochromatic source of light S is kept equidistant from the slits S2 and S2. Explain the formation of dark and bright fringes on the screen.
(b) A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in Young’s double-slit experiment.
(i) Find the distance of the third bright fringe on the screen from the central maximum for wavelength 650 nm?
(ii) What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide?
Given : the separation between the slits is 4 mm and the distance between the screen and plane of the slits is 1.2 m. (Comptt. Delhi 2016)
Question 6.
Find an expression for intensity of transmitted light when a polaroid sheet is rotated between two crossed polaroids. In which position of the Polaroid sheet will the transmitted intensity be maximum? (Delhi 2015)
Question 7.
Answer the following questions:
(i) In a double slit experiment using light of wavelength 600 nm, the angular width of the fringe formed on a distant screen is 0.1°. Find the spacing between the two slits.
(ii) Light of wavelength 5000 A propagating in air gets partly reflected from the surface of water. How will the wavelengths and frequencies of the reflected and refracted light be affected? (Delhi 2015)
Question 8.
State clearly how an unpolarised light gets linearly polarised when passed through a Polaroid.
(i) Unpolarised light of intensity I0 is incident on a polaroid P1 which is kept near another Polaroid P2 whose pass axis is parallel to that of P1. How will the intensities of light, I1 and I2, transmitted by the polaroids P1 and P2 respectively, change on rotating Px without disturbing P2?
(ii) Write the relation between the intensities I1 and I2. (All India 2015)
Question 9.
Use Huygens’ principle to show how a plane wavefront propagates from a denser to rarer medium. Hence verify Snell’s law of refraction. (All India 2015)
Question 10.
Explain by drawing a suitable diagram that the interference pattern in a double slit is actually a superposition of single slit diffraction from each slit.
Write two basic features which distinguish the interference pattern from those seen in a coherently illuminated single slit. (Comptt. Delhi 2015)
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