FRICTION & PHYSICAL OPTICS
FRICTION & PHYSICAL OPTICS
1. In the case of an achromatic prism, there is..
1) deviation without dispersion 2) dispersion without deviation
3) refraction without deviation 4) dispersion and deviation
2. A red ray is deviated by two prisms at angles 10° and 8° respectively. The two prisms deviate blue ray at angles 12° and 10° respectively. Their dis-persive powers will be in the ratio
1) 11 : 9 2) 9 : 11
3) 3 : 2 4) 1 : 1
3. The angular dispersion produced by a prism
1) Increases if the average refractive index decreases
2) Increases if the average refractive index increases
3) Remains constant for any two colours
4 Is independent of refractive index of material
4. Consider the following state-ments
(A) Absorption spectrum is due to the absorption of matter by radiation
(B) Line spectrum is due to the electronic transition from higher orbits to lower orbits
1) Both A and B are correct
2) A is correct B is wrong
3) A is wrong B is correct 4) Both A and B are incorrect
5. The ratio of the angles of deviation of a monochromatic light ray when it passes through a small angled prism of refractive index 1.5 in air, with that of immersed in a liquid of refractive index 1.2 is
1) 1 : 2 2) 2 : 1
3) 5 : 4 4) 5 : 2
6. In the case of diffraction of light at straight edge
1) There is absolute darkness in the geometrical shadow
2) There is a faint light whose intensity is uniform
3) There are alternately dark and bright bands of decreasing intensity
4) There is a faint light whose intensity gradually becomes zero
7. [A]: Diffraction phenomenon is much harder to observe in light than in sound.
[R]: Wavelength of light is smaller than that of sound in comparison with size of obs-tacles.
1) Both A and R are true and R is the correct explanation of A
2) Both A and R are true but R is not the correct explanation of A
3) A is true but R is false
4) A is false but R is true
8. In the propagation of electro-magnetic waves, the angle bet-ween direction of propagation and plane of polarization is
1) 0° 2) 180° 3) 90° 4) 45°
9. From Brewster's law of polari-zation it follows that angle of polarization depends upon
1) Wavelength of light
2) Orientation of plane of vibration
3) Orientation of plane of polarization
4) Angle of deviation
10. A rays of light in air is incident on a glass plate at polarizing angle. It suffers a deviation of 22° on entering glass. The angle of polarization is
1) 90° 2) 56° 3) 68° 4) 34°
11. If the critical angle for a crystal is 45° w.r. to air, its polarizing angle is
1) tan-1(2) 2) tan-1(1/2) 3) tan-1 4) tan-1
12. If polarizing angle for a crystal is 54° then, in the arrangement of pile of such crystals to produce polarized light by refraction, the planes must be inclined to the axis at an angle of
1) 36° 2) 27°
3) 18° 4) 32.5°
14. Two waves having intensities I and 4I produce interference pattern. The ratio of intensities at two points on the screen where phase difference bet-ween the waves are p/2 and p/3 respectively is
1) 5 : 1 2) 5 : 7
3) 5 : 9 4) 3 : 2
15. In the figure, S1 and S2 are coherent sources. The intensity of both sources is same. If the intensity at the point 'p' is 4 watt/m2, the intensity of each source is
1) 1 watt/m2 2) 2 w/m2
3) 3 w/m2 4) 4 w/m2
16. When 'n' in coherent sources each of intensity I0 are super imposed at a point, the inten-sity at that point is I1. If the 'n' sources are coherent, the resul- tant intensity is I2. Then I2: I1 =
1) 1 : n2 2) 1 : Ön
3) n : 1 4) n : Ön
17. A wave front and a ray of light are
1) Perpendicular to each other
2) Parallel to each other
3) Convergent towards each other
4) Divergent from each other
18. If polychromatic light is used in Young's double slit experi-ment then out of the following the wrong one is
1) Central fringe is white with alternate coloured bands on either sides of it
2) Central fringe is white su-rrounded by bands of variable fringe width
3) No interference pattern is ob-served on the screen
4) Order of the fringe width varies with order of the fringe
19. In Young's double slit experi-ment it one of the slits is covered with opaque black paper then we observe
1) Interference pattern with less intensity at bright fringes is obtained
2) Interference pattern with more darkness at dark fringes is obtained
3) Uniform intensity with a reduction of half of the initial intensity of a source
4) Uniform intensity with a re-duction of 4 times of the initial intensity of bright bands
20. In Young's double slit experi-ment
1) Only interference occurs
2) Only diffraction occurs
3) Both interference and diffra-ction occurs
4) Interference and polarization occurs
21. A wooden box of mass 50 kg is on a horizontal surface ms = 0.5, mk = 0.4. If a horizontal force of 150 N is acting on the box, then frictional force on the box is
1) 150 N 2) 245 N
3) 196 N 4) 49 N
22. A uniform chain of linear den-sity 2 kg/m lies at rest on a horizontal table with 32 cm of it hanging over the edge. If ms = 0.8 then total mass of the chain is
1) 0.72 kg 2) 2.88 kg 3) 0.36 kg 4) 1.44 kg
23. A particle is projected up a 45° incline with velocity 'V'. It returns back to the starting point with speed V1 then
(V1 / V) = ? (mk = 0.5)
1) 1 : 3 2) 3 : 1
3) 1 : 3 4) 1 : 1
24. A body which is pushed and released along a horizontal surface moves with a retar-dation of g/4. The coefficient of friction is
1) 0.2 2) 0.1 3) 0.25 4) 0.75
25. A block of mass 2 kg is placed on the inclined plane of height 4 m and length 5 m. To keep it in equilibrium it is pressed with a force 'F' perpendicular to the plane. Minimum value of that force is (m = 0.4, g = 10 ms-2)
1) 14 N 2) 28 N
3) 7 N 4) 21 N
26. A block of mass 'm' rests on a rough horizontal surface as shown. Coefficient of friction between the block and the surface is m. A force F= mg acting at angle q with vertical pulls it. The condition under which the block moves is
1) tan q ³ m 2) cotq ³ m
3) tan(q /2) ³ m 4) cot(q/2) ³ m
KEY
1) 1 2) 2 3) 2 4) 3
5) 2 6) 4 7) 1 8) 3
9) 1 10) 2 11) 3 12) 1
13) 2 14) 2 15) 1 16) 3
17) 1 18) 3 19) 4 20) 3
21) 1 22) 4 23) 3 24) 3
25) 2 26) 4
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