# Optics

1. A vessel of depth t is half filled with oil of refractive index µ1, and the other half is filled with water of refractive index µ2. The apparent depth of the vessel when viewed from above is 2. Two glasses have dispersive powers in the ratio of 2 : 3. These glasses are used in the manufacture of an achromatic objective of focal length 20 cm. Then the focal lengths of the two lenses of the objective are
1) 12.5 cm, −20 cm         2) 6.67 cm, −10 cm            3) 15 cm, −20 cm            4) +10 cm, −10 cm

3. A small plane mirror is placed at the centre of a spherical screen of radius R. A beam of light is  falling on the mirror. If the  mirror makes n revolutions per second, the speed of  the spot of light on the screen after reflection from the  mirror will be 4. The refracting angle of a prism is A and the refractive index is cot (A/2).Then the angle of minimum deviation is
1) 180° − 4A             2) 180° − 3A             3) 180° − 2A             4) 180° − A

5. In the visible region, the dispersive powers and the mean angular deviations, for crown and flint glass prisms  are ω, ω' and d, d' respectively. When the two prisms are combined, the condition of zero dispersion by the combination is 6. A short linear object of length l lies on the axis of a concave mirror of focal length f at a distance u from the pole. Then the length of image will be 7. A convex lens of focal length f is placed between an object and a screen. If the distance between the screen and the object is greater than 4f, we can obtain a sharp image of the object on the screen for two positions L1 and L2 of the lens. These are conjugate positions. In one case the image is magnified and in the other case it is diminished. If h1, h2 are the heights of the two images, then the height of the object is 8. The two slits in Yong's interference experiment have widths in the ratio n : 1. The ratio of the intensities of the maxima and minima in the interference pattern is  9. In an interference experiment, 20th order maximum is observed at a point on the screen  when light of wavelength 480 nm is used. If this light is replaced by a light of wavelength 600 nm, then the order of the maximum at the same point will be
1) 10             2) 12              3) 14              4) 16

10. In Yong's double slit experiment sodium light composed of two wavelengths  λ1 and λ2 close to each other  ( λ2 > λ1 ) is used. The order n upto which the fringes can be seen on the screen is 11. A parallel beam of monochromatic light of wavelength λ falls normally on a narrow slit of width a. The diffraction pattern is observed on a screen placed perpendicular to the direction of the incident beam. The phase difference between the waves coming from the edges of the slit at the position of the first maximum of the diffraction pattern is 12. A man is walking under an inclined mirror at a constant velocity V ms−1 along the X-axis. If the mirror is inclined at an angle θ with the horizontal, then the velocity of the image is...  13. A car is fitted with a convex mirror of focal length 20 cm. A second car 2 m broad and 1.6 m high is 6 m away from the first car. Then the position of the second car as seen in the mirror of the first car is....
1) 21.48 cm              2) 19.35 cm            3) 20.50 cm               4) 30 cm

14. A ray of light is incident on a glass sphere of refractive index 3/2. What should be the angle of incidence so that the ray which enters the sphere doesn't come out of the sphere
1) 30°             2)  60°             3)  90°               4)  45°

15. A, B and C are three optical media of respective critical angles C1, C2 and C3. Total internal reflection of light can occur from A to B, also from B to C but not from C to A. Then the relation between C1, C2 and C3 is...
1) C1< C2< C3            2) C1 > C2 > C3
3) C1 = C2 > C3           4)  C1 > C2 = C3

16.  When an object is kept at a distance of 30 cm from a concave mirror, the image is formed at a distance of 10 cm. If the object is moved with a speed of 9 cms−1, the speed with which the image moves is
1) 9 cms−1          2) 6 cms−1         3) 3 cms−1          4) 1 cms−1

17. A ray of light from a denser medium strikes a rarer medium at an angle of incidence i. The reflected and refracted rays make an angle π/2 with each other. If the angles of reflection and refraction are r and r', Then the critical angle is
1) sin−1 (tan r)          2)  sin−1 (tan i)              3) sin−1 (Sin r)           4) tan−1 (sin i)

18. The lateral magnification of the lens with an object located at two different positions u1 and u2 are m1 and m2 respectively. Then the focal length of the lens is 19. A gun of mass m1 fires a bullet of mass m2 with a horizontal speed V. The gun is fitted with a concave mirror of focal length f facing toward a receding bullet. The speed of separation of the bullet and the image just after the gun was fired 20. A rod made of glass, refractive index 1.5 and of square cross section, is bent into the shape as shown in the figure.  A parallel beam of light falls normally on the plane flat surface A.  'd' and 'R' represents width of a side and radius of the inner semi - circle. Then  the maxi mum value of ratio d/R so that all light entering the glass through surface A emerges from the glass through surface B is  21. A point object is kept in front of a plane mirror. The plane mirror is doing SHM of amplitude 2 cm. The plane mirror moves along the X-axis which is normal to the mirror. The amplitude of the mirror is such that the object is always in front of the mirror. The amplitude of SHM of the image is
1) 0 cm          2)  1 cm          3)  2 cm          4) 4 cm

22. A clear transparent glass sphere (µ = 1.5) of radius R is immersed in a liquid of refractive index 1.25. A parallel beam of light incident on it will converge to a point. The distance of this point from the centre will be
1) +R         2)  −R            3)  +3R            4) −3R

23. A circular beam of light of diameter d = 2 cm falls on a plane surface of a glass.  The angle of Incidence is 60° and refractive index of glass is µ = 3/2. Then the diameter of the refracted beam is
1) 3 cm            2)  3.26  cm          3) 4 cm          4) 4.26 cm

24. In Young's double slit experiment, the intensity of light at a point on the screen, where the path difference is λ, is I. The intensity of light at a point where the path difference becomes λ/3 is 25. In Young's double slit experiment, having slits of equal width, let β be the fringe width and I0 be the maximum intensity. At a distance x from the central bright fringe, the intensity will be 26. Light of wave length λ0 in air enters a medium of refractive Index µ. If two points A and B in this medium lie along the path of this light at a distance x, then phase difference between these two points is 27. A convex lens forms a real image of a point object at a distance 50 cm from the convex lens. A concave lens is placed 10 cm behind the convex lens on the image side. On placing a plane mirror on the image side and facing the concave lens, it is observed that the final image now coincides with the object itself.  Then the focal length of the concave lens is
1) 20 cm               2) 30 cm              3) 40 cm             4) 50 cm

28. An equiconvex lens is made from glass of refractive index 1.5.  If the radius of each surface is changed from 5 cm to 6 cm, then the power
1) Increases by 3.33 D            2)  Decreases by 3.33 D
3) Decreases by 1 D            4) Remains uncharged

29. A point object is placed at a distance of 25 cm from a convex lens of focal length 20 cm. If a glass slab of thickness t and refractive index 1.5 is inserted between the lens and the object, the image is formed at infinity. Then the thickness t is
1) 5 cm          2)  10 cm         3) 15 cm            4) 20 cm

30. A small piece of wire bent into an L-shape, with upright and horizontal portions of equal lengths, is placed with the horizontal portion along the axis of a concave mirror whose radius of curvature is 10 cm. If the bend is 20 cm from  the pole of the mirror, than the ratio of the lengths of the images of the upright and horizontal portions of the wire is
1) 1 : 2              2)  2 : 1            3) 1 : 3              4)  3 : 1

ANSWERS: 1-1; 2-2; 3-4; 4-3; 5-1; 6-4; 7-4; 8-2; 9-4; 10-3; 11-4; 12-4; 13-2; 14-3; 15-1; 16-4; 17-2; 18-4; 19-2; 20-1; 21-4; 22-3; 23-2; 24-4; 25-2; 26-3; 27-3; 28-2; 29-3; 30-4.

Posted Date : 12-04-2021

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గమనిక : ప్రతిభ.ఈనాడు.నెట్‌లో కనిపించే వ్యాపార ప్రకటనలు వివిధ దేశాల్లోని వ్యాపారులు, సంస్థల నుంచి వస్తాయి. మరి కొన్ని ప్రకటనలు పాఠకుల అభిరుచి మేరకు కృత్రిమ మేధస్సు సాంకేతికత సాయంతో ప్రదర్శితమవుతుంటాయి. ఆ ప్రకటనల్లోని ఉత్పత్తులను లేదా సేవలను పాఠకులు స్వయంగా విచారించుకొని, జాగ్రత్తగా పరిశీలించి కొనుక్కోవాలి లేదా వినియోగించుకోవాలి. వాటి నాణ్యత లేదా లోపాలతో ఈనాడు యాజమాన్యానికి ఎలాంటి సంబంధం లేదు. ఈ విషయంలో ఉత్తర ప్రత్యుత్తరాలకు, ఈ-మెయిల్స్ కి, ఇంకా ఇతర రూపాల్లో సమాచార మార్పిడికి తావు లేదు. ఫిర్యాదులు స్వీకరించడం కుదరదు. పాఠకులు గమనించి, సహకరించాలని మనవి.