12th Standard Physics English Medium Wave Optics Reduced Syllabus Important Questions 2021

12th Standard

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Physics

Time : 01:00:00 Hrs
Total Marks : 100
Multiple Choice Questions
10 x 1 = 10
1. A plane glass is placed over a various coloured letters (violet, green, yellow, red) The letter which appears to be raised more is,

(a)

red

(b)

yellow

(c)

green

(d)

violet

2. In a Young’s double-slit experiment, the slit separation is doubled. To maintain the same fringe spacing on the screen, the screen-to-slit distance D must be changed to,

(a)

2D

(b)

$\frac{D}{2}$

(c)

$\sqrt{2}$D

(d)

$\frac{D}{\sqrt2}$

3. Two coherent monochromatic light beams of intensities I and 4I are superposed. The maximum and minimum possible intensities in the resulting beam are

(a)

5I and I

(b)

5I and 3I

(c)

9I and I

(d)

9I and 3I

4. When light is incident on a soap film of thickness 5×10–5 cm, the wavelength of light reflected maximum in the visible region is 5320 Å. Refractive index of the film will be,

(a)

1.22

(b)

1.33

(c)

1.51

(d)

1.83

5. First diffraction minimum due to a single slit of width 1.0×10–5 cm is at 30o. Then wavelength of light used is,

(a)

400 $\mathring { A }$

(b)

500 $\mathring { A }$

(c)

600 $\mathring { A }$

(d)

700 $\mathring { A }$

6. A ray of light strikes a glass plate at an angle 60o. If the reflected and refracted rays are perpendicular to each other, the refractive index of the glass is,

(a)

$\sqrt3$

(b)

$\frac{3}{2}$

(c)

$\sqrt{\frac{3}{2}}$

(d)

2

7. One of the of Young’s double slits is covered with a glass plate as shown in figure. The position of central maximum will,

(a)

get shifted downwards

(b)

get shifted upwards

(c)

will remain the same

(d)

data insufficient to conclude

8. Light transmitted by Nicol prism is,

(a)

partially polarised

(b)

unpolarised

(c)

plane polarised

(d)

elliptically polarised

9. The transverse nature of light is shown in,

(a)

interference

(b)

diffraction

(c)

scattering

(d)

polarisation

10. A rear mirror of a vehicle is cylindrical having radius of curvature 10 cm. The length of arc of curved surface is also 10 cm. If the eye of driver is assumed to be at large distance, from the mirror, then the field of view in radian is

(a)

0.5

(b)

1

(c)

2

(d)

4

11. 2 Marks
10 x 2 = 20
12. What are the salient features of corpuscular theory of light?

13. Write a short note on quantum theory of light.

14. State Huygens’ principle

15. What are coherent sources?

16. Differentiate between Fresnel and Fraunhofer diffraction.

17. What is a diffraction grating?

18. Differentiate between polarised and unpolarised light.

19. What are polariser and analyser?

20. State and obtain Malus' law.

21. What is astigmatismt?

22. 3 Marks
10 x 3 = 30
23. Prove law of reflection using Huygens' principle.

24. Discuss the interference in thin films and obtain the equations for constructive and destructive interference for transmitted and reflected light.

25. Discuss the diffraction at a grating and obtain the condition for the mth maximum.

26. Discuss the experiment to determine the wavelength of different colours using diffraction grating.

27. Obtain the equation for resolving power of optical instrument.

29. Obtain the equation for bandwidth in Young's double slit experiment,

30. Write the conditions for obtaining clear and broad interference bands

31. What is Airy's discs

32. Write the drawbacks of Nicol prism.

33. 5 Marks
8 x 5 = 40
34. A beam of light of wavelength 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. What is the distance between the first dark fringe on either side of the central bright fringe?

35. You are given two converging lenses of focal lengths 1.25 cm and 5 cm to design a compound microscope. If it is desired to have a magnification of 30, find out the seperation between the objective and the eyepiece

36. A Parallel beam of light of 500 nm falls on a narrow slit and be resulting diffraction pattern is observed on a screen 1m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Calculate the width of the slit.

37. In Young's double slit experiment monochromatic ligt of wavelength 630 nm illuminates the pair of slits and produces an interference pattern in which two consecutive bring fringes are separated by 8.1 mm. Anther 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 in the monochromatic source is replaced by a source of white light?

38. In double slit experiment, SS2 is greater than SSI by 0.25 A • Calculate the path difference between two interfering beams from SI and S2 for minima and maxima on the screen.

39. Two polaroids are set in crossed positions. A third polaroid is placed between the two making an angle e with the pass axis of the first polaroid. Write the expression for the intensityof light transmitted from the second polaroid. In what orientations will the transmitted intensity be (i) minimum and (ii) maximum.

40. If a particle is thrown horizontally at a speed of 3x 108ms-1, deduce the verticalfall in traveling 1 km distance. Given: g = 10 ms-2, Does that result depend upon the mass of the particle? Comment on your result, considering that Newton thought light is made up of corpuscles that at a very large speed by the source

41. Prove the laws of reflection using Huygen's principle.