Class 12 Physics Chapter 9 Ray Optics and Optical Instruments MCQ Questions with Answers

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Class 12 Ray Optics and Optical Instruments with Answers

Class 12 Physics MCQ with answers are given here to Ray Optics and Optical Instruments. These MCQs are based on the latest CBSE board syllabus and relate to the latest Class 12 Physics syllabus. By Solving these Class 12 MCQs, you will be able to analyze all of the concepts quickly in the chapter and get ready for the Class 12 Annual exam.

Learn Class 12 Ray Optics and Optical Instruments MCQ Questions with Answers PDF download according to the latest CBSE and NCERT syllabus. Students should prepare for the examination by solving CBSE MCQ on Ray Optics Class 12 PDF given below.

Question 1. How can the chromatic aberration be corrected    
(a) By providing different suitable curvature to its two surface
(b) By combining it with another lens of opposite nature
(c) By reducing its aperture
(d) By providing proper polishing of its two surfaces

Question 2. When a beam of light from air enters into the water, the characteristics of light will not be changed, is :     
(a) frequency
(b) speed
(c) colour
(d) amplitude

Question 3. If two mirrors are kept at 45° to each other and a body is placed in the middle then total number of images formed is :   
(a) 7
(b) 8
(c) 14
(d) 4

Question 4. An astronomical telescope of ten fold angular magnification has a length of 44 cm. The focal length of the objective is :   
(a) 44 cm
(b) 440 cm
(c) 40 cm
(d) 4 cm

Question 5. The refractive index of diamond is 2.0, velocity of light in diamond in cm per second is approximately :    
(a) 1.5 × 10¹⁰
(b) 2.0 × 10¹⁰
(c) 6 × 10¹⁰
(d) 3 × 10¹⁰

Question 6. The critical angle for the material of a prism is 45°and its refracting angle is 30°. A monochromatic ray goes out perpendicular to the surface of emergence from the prism. Then the angle of incidence on the prism will be :   
(a) 60°
(b) 75° 
(c) 45°
(d) 30°

Question 7. Mirage is a phenomenon due to :     
(a) refraction of light
(b) diffraction of light
(c) total internal reflection of light
(d) none of these

Question 8. In an astronomical microscope, the focal length of the objective is made : 
(a) shorter than that of the eye piece
(b) greater than that of the eye piece
(c) half of the eye piece
(d) equal to that of the eye piece

Question 9. Light appears to travel in a straight line, because 
(a) its wavelength is very small 
(b) its velocity is large
(c) it is not absorbed by surroundings
(d) it is reflected by surroundings

Question 10. Sky appears to be blue in clear atmosphere due to which property of light :   
(a) Scattering
(b) Polarization
(c) Diffraction
(d) Dispersion

Question 11. A doctor prescribes spectacles to a patient with a combination of a convex lens of focal length 40 cm, and concave lens of focal length 25 cm then the power of spectacles will be : 
(a) – 6.5 D
(b) 1.5 D
(c) – 1.5 D
(d) – 8.5 D

Question 12. When a ray of light enters a glass slab, then    
(a) its frequency and wavelength changes
(b) its frequency does not change
(c) only frequency changes
(d) its frequency and velocity changes

Question 13. An equilateral prism is made of a material of refractive index 3 . The angle of minimum deviation for the prism is     
(a) 90°
(b) 60°
(c) 45°
(d) 30°

Question 14. A concave mirror having the focal length 15 cm, forms an image having twice of the linear dimensions of the object. If the image is virtual, then the position of the object will be : 
(a) 7.5 cm
(b) 22.5 cm
(c) 40 cm
(d) 30 cm

Question 15. Four lenses having the focal length of + 15 cm, 20 cm, +150 cm, and +250 cm respectively are provided to make an astronomical telescope. The focal length of the eyepiece to produce the largest magnification, should be :  
(a) + 250 cm
(b) + 155 cm
(c) 25 cm
(d) + 15 cm

Question 16. The Cauchy’s dispersion formula is    
(a) h = A + B l2 + Cl4
(b) μ = A + B l–2 + Cl4
(c) μ = A + B l2 + Cl–4
(d) μ = A + B l–2 + Cl–4

Question 17. An object is immersed in a fluid. In order that the object becomes invisible, it should :    
(a) behave as a perfect reflector
(b) absorb all light falling on it
(c) have refractive index one
(d) have refractive index exactly matching with that of the surrounding fluid

Question 18. Sodium lamps are used in foggy conditions because :    
(a) yellow light is scattered less by the fog particles
(b) yellow light is scattered more by the fog particles
(c) yellow light is unaffected during its passage through the fog
(d) Wavelength of yellow light is the mean of the visible part of the spectrum

Question 19. In refraction, light waves are bent on passing from one medium to the second medium, because, in the second medium:    
(a) the frequency is different
(b) the coefficient of elasticity is different
(c) the speed is different
(d) the amplitude is smaller

Question 20. 1 wire mesh consisting of very small squares is viewed at a distance of S cm through a magnifying converging lens of focal length 10 cm, kept close to the eye. The magnification produced by the lens is:    
(a) 5
(b) 8
(c) 10
(d) 20

Question 21. An achromatic convergent lens of focal length 20 cms is made of two lenses (in contact) of materials having dispersive powers in the ratio of 1 : 2 and having focal lengths f1 and f2. Which of the following is true ? 
(a) f1 = 10 cms, f2 = –20 cms
(b) f1 = 20 cms, f2 = 10cms
(c) f1 = –10 cms, f2 = –20 cms
(d) f1 = 20 cms, f2 = –20 cms

Question 22. A ray of light is incident at an angle of incidence, i, on one face of prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is m, the angle of incidence i, is nearly equal to 
(a) μA
(b) μA/2
(c) μ/A
(d) A/2μ

Question 23. A lens is made of flint glass (refractive index = 1.5). When the lens is immersed in a liquid of refractive index 1.25, the focal length:    
(a) increases by a factor of 1.25
(b) increases by a factor of 2.5
(c) increases by a factor of 1.2
(d) decreases by a factor of 1.2

Question 24. A leaf which contains only green pigments, is illuminated by a laser light of wavelength 0.6328 mm. It wound appear to be:    
(a) brown
(b) black
(c) red
(d) green

Question 25. The focal length of the objective and eye lenses of a microscope are 1.6 cm and 2.5 cm respectively.  
The distance between the two lenses is 21.7 cm.
If the final image is formed at infinity, what is the linear magnification? 
(a) 11
(b) 110
(c) 1.1
(d) 44

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Question 26. The camera lens has an aperture of f and the exposure time is (1/60)s. What will be the new exposure time if the aperture become 1.4 f ?    
(a) 1/42
(b) 1/56
(c) 1/72
(d) 1/31

Question 27. A thin glass (refractive index 1.5) lens has optical power of – 5 D in air. Its optical power in a liquid medium with refractive index 1.6 will be    
(a) – 1D
(b) 1 D
(c) – 25 D
(d) 25 D

Question 28. A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of this circle in cm is   
(a) 36/√7
(b) 36 √7
(c) 4√ 5
(d) 36 √5

Question 29. A fish in an aquarium, 30 cm deep in water can see a light bulb kept 50 cm above the surface of water. The fish can also see the image of this bulb in the reflecting bottom surface of the aquarium. Total depth of water is 60 cm. Then the apparent distance between the two images seen by the fish is (mw = 4/3)     
(a) 140 cm
(b) 760/3 cm
(c) 280/3 cm
(d) 380/3 cm

Question 30. The focal length of the objective and eye piece of a telescope are respectively 200 cm and 5 cm.  The maximum magnifying power of the telescope will be 
(a) – 100
(b) – 60
(c) – 48
(d) – 40

Question 31. A thin prism P1 with angle 6° and made froM glass of refractive index 1.54 is combined with another thin prism P2 of refractive index 1.72 to produce dispersion without deviation. The angle of prism P2 will be    
(a) 4° 30′
(b) 8.5°
(c) 6.5°
(d) none of these

Question 32. The focal length of a converging lens are fV and fR for violet and red light respectively. Then   
(a) fV > fR
(b) fV = fR
(c) fV < fR
(d) any of the three is
possible depending on the value of the average refractive index m

Question 33. A plano-convex lens of focal length 30 cm has its plane surface silvered. An object is placed 40 cm from the lens on the convex side. The distance of the image from the lens is  B
(a) 18 cm
(b) 24 cm
(c) 30 cm
(d) 40 cm

Question 34. An endoscope is employed by a physician to view the internal parts of a body organ. It is based on the principle of :    
(a) refraction
(b) reflection
(c) total internal reflection
(d) dispersion

Question 35. A telescope has an objective lens of focal length 200 cm and an eye piece with focal length 2 cm.
If this telescope is used to see a 50 metre tall building at a distance of 2 km, what is the height of the image of the building formed by the objective lens?    
(a) 5 cm
(b) 10 cm
(c) 1 cm
(d) 2 cm

Question 36. A man 160 cm high stands in front of a plane mirror. His eyes are at a height of 150 cm from the floor. Then the minimum length of the plane mirrorfor him to see his full length image is  C
(a) 85 cm
(b) 170 cm
(c) 80 cm
(d) 340 cm

Question 37. A green light is incident from the water to the air – water interface at the critical angle (q). Select the correct statement.    
(a) The entire spectrum of visible light will come out of the water at an angle of 90º to the normal.
(b) The spectrum of visible light whose frequency is less than that of green light will come out to the air medium.
(c) The spectrum of visible light whose frequency is more than that of green light will come out to the air medium.
(d) The entire spectrum of visible light will come out of the water at various angles to the normal.

Question 38. In total internal reflection when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction?
(a) 90°
(b) 180°
(c) 0°
(d) equal to angle of incidence 

Question 39. Which of the following is not due to total internal reflection?
(a) Working of optical fibre
(b) Difference between apparent and real depth of a pond
(c) Mirage on hot summer days
(d) Brilliance of diamond 

Question 40. A ray of light travelling in a transparent medium of refractive index m, falls on a surface separating the medium from air at an angle of incidence of 45°. For which of the following value of m the ray can undergo total internal reflection?
(a) m = 1.33
(b) m = 1.40
(c) m = 1.50
(d) m = 1.25

Question 41. Which of the following is false ?
(a) Convex lens always forms image with m < 1
(b) A simple mirror produces virtual, erect and same-sized image
(c) A concave mirror produces virtual, erect and magnified image
(d) A convex lens can produce real and same-sized image

Question 42. Which of the following is not the case with the image formed by a concave lens?
(a) It may be erect or inverted
(b) It may be magnified or diminished
(c) It may be real or virtual
(d) Real image may be between the pole and focus or beyond focus

Question 43. The intensity produced by a long cylindrical light source at a small distance r from the source is proportional to
(a) 1/r²
(b) 1r³
(c) 1/r
(d) None of these

Question 44. Two thin lenses of focal lengths f₁ and f₂ are in contact and coaxial. Its power is same as power of a single lens given by

(a)

(b)

(c)

(d)

Question 45. An astronomical telescope has a large aperture to
(a) reduce spherical aberration
(b) have high resolution
(c) increase span of observation
(d) have low dispersion

Question 46. A lamp of 250 candle power is hanging at a distance of 6 m from a wall. The illuminance at a point on the wall at a minimum distance from lamp will be
(a) 9.64 lux
(b) 4.69 lux
(c) 6.94 lux
(d) None of these

Question 47. The critical angle for light going from medium X into medium Y is q. The speed of light in medium X is v, then speed of light in medium Y is
(a) v(1 – cos θ)
(b) v/sin θ
(c) v/cos θ
(d) v cos θ

Question 48. The refractive index of a piece of transparent quartz is the greatest for
(a) violet light
(b) red light
(c) green light
(d) yellow light

Question 49. Critical angle of light passing from glass to water is minimum for
(a) red colour
(b) green colour
(c) yellow colour
(d) violet colour

Question 50. A plane mirror reflects a beam of light to form a real image. The incident beam is
(a) parallel
(b) convergent
(c) divergent
(d) any one of the above

Question 51. A ray of light incident at an angle q on a refracting face of a prism emerges from the other face normally. If the angle of the prism is 5° and the prism is made of a material of refractive index 1.5, the angle of incidence is
(a) 7.5°
(b) 5°
(c) 15°
(d) 2.5°

Question 52. An object approaches a convergent lens from the left of the lens with a uniform speed 5 m/s and stops at the focus. The image
(a) moves away from the lens with an uniform speed 5 m/s
(b) moves away from the lens with an uniform acceleration
(c) moves away from the lens with a non-uniform acceleration
(d) moves towards the lens with a non-uniform acceleration

Question 53. A short pulse of white light is incident from air to a glass slab at normal incidence. After travelling through the slab, the first colour to emerge is
(a) blue
(b) green
(c) violet
(d) red

Question 54. A passenger in an aeroplane shall
(a) never see a rainbow
(b) may see a primary and a secondary rainbow as concentric circles
(c) may see a primary and a secondary rainbow as concentric arcs
(d) shall never see a secondary rainbow

Question 55. The radius of curvature of the curved surface of a planoconvex lens is 20 cm. If the refractive index of the material of the lens be 1.5, it will
(a) act as a convex lens only for the objects that lie on its curved side
(b) act as a concave lens for the objects that lie on its curved side
(c) act as a convex lens irrespective of the side on which the object lies
(d) act as a concave lens irrespective of side on which the object lies

Question 56. You are given four sources of light each one providing a light of a single colour – red, blue, green and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is 90°. Which of the following statements is correct if the source of yellow light is replaced with that of other lights without changing the angle of incidence?
(a) The beam of red light would undergo total internal reflection
(b) The beam of red light would bend towards normal while it gets refracted through the second medium
(c) The beam of blue light would undergo total internal reflection
(d) The beam of green light would bend away from the normal as it gets refracted through the second medium

Question 57. The phenomena involved in the reflection of radiowaves by ionosphere is similar to
(a) reflection of light by a plane mirror
(b) total internal reflection of light in air during a mirage
(c) dispersion of light by water molecules during the formation of a rainbow
(d) scattering of light by the particles of air

Question 58. The optical density of turpentine is higher than tnat of water while its mass density is lower. Figure shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in figure, the path shown is correct?
(a) 1
(b) 2
(c) 3
(d) 4

Question 59. The direction of ray of light incident on a concave mirror is shown by PQ while directions in which the ray would travel after reflection is shown by four rays marked 1, 2, 3 and 4 (figure). Which of the four rays correctly shows the direction of reflected ray?

(a) 1
(b) 2
(c) 3
(d) 4

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