JEE Physics Ray Optics and Optical Instruments MCQs Set A

Question. Digital movie projectors work on the principle of
(a) Reflection from micromirrors
(b) Dispersion from thin prisms
(c) Refraction from thin lenses
(d) Total internal reflection from optical fibres

Answer: A

Question. Day and night settings for rearview mirrors uses
(a) Thick wedge shaped mirrors
(b) Concave mirrors
(c) Thin mirrors
(d) Convex mirrors

Answer: A

Question. When a beam of light is incident on a plane mirror, it is found that a real image is formed. The incident beam must be
(a) Converging
(b) Diverging
(c) Parallel
(d) Formation of real image by a plane mirror is impossible

Answer: A

Question. An object is placed symmetrically between two plane mirrors, inclined at an angle of 72°, then the total number of images observed is
(a) 4
(b) 5
(c) 2
(d) Infinite

Answer: A

Question. A person 1.6 m tall is standing at the centre between two walls three metre high. What is the minimum size of a plane mirror fixed on the wall in front of him, if he is to see the full height of the wall behind him?
(a) 1 m
(b) 0.8 m
(c) 1.5 m
(d) 2.3 m

Answer: A

Question. While capturing solar energy for commercial purposes we use
(a) Parabolic mirrors
(b) Plane mirrors
(c) Convex mirrors
(d) Concave mirrors

Answer: A

Question. A convex mirror is used to form an image of a real object. Then mark the wrong statement
(a) The image is real
(b) The image is diminished in size
(c) The image lies between the pole and focus
(d) The image is erect

Answer: A

Question.  A convex mirror has a focal length f. A real object is placed at a distance f in front of it, from the pole. It produces an image at
(a) f/2
(b) f
(c) Infinity
(d) 2f

Answer: B

Question. An object placed in front of a concave mirror of focal length 0.15 m produces a virtual image, which is twice the size of the object. The position of the object with respect to the mirror is
(a) –7.5 cm
(b) –8.5 cm
(c) –6.5 cm
(d) –5.5 cm

Answer: A

Question. When a light ray from a rarer medium is refracted into a denser medium, its
(a) Speed decreases, wavelength decreases
(b) Speed decreases, wavelength increases
(c) Speed increases, wavelength increases
(d) Speed increases, wavelength decreases

Answer: A

Question. Which of the following phenomenon of light forms a rainbow?
(a) Reflection as well as refraction
(b) Refraction
(c) Reflection of light
(d) Total internal reflection

Answer: B

Question. Which of the following is possible application of fibre optics?
(a) All of the above
(b) High speed internet traffic
(c) Endoscopy
(d) Radio, TV & Telephone signals

Answer: A

Question. An object is placed at a distance of f/2 from a convex lens. The image will be
(a) At one of the foci, virtual and double its size
(b) At 3f/2, real and inverted
(c) At f, real and inverted
(d) At 2f, virtual and erect

Answer: A

Question. The least distance between a point object and its real image formed by a convex lens of focal length F is
(a) 4 F
(b) 3 F
(c) 2 F
(d) Greater than 4 F

Answer: A

Question. The plane faces of two identical plano-convex lenses, each having focal length of 40 cm, are placed against each other to form a usual convex lens. The distance from this lens at which an object must be placed to obtain a real, inverted image with magnification '–1' is
(a) 40 cm
(b) 80 cm
(c) 20 cm
(d) 160 cm

Answer: A

Question. Two thin lenses of focal lengths 20 cm and –20 cm are placed in contact with each other. The combination has a focal length equal to
(a) Infinite
(b) 50 cm
(c) 60 cm
(d) 10 cm

Answer: A

Question. If in a plano-convex lens, radius of curvature of convex surface is 10 cm and the focal length of lens is 30 cm, the refractive index of the material of the lens will be
(a) 1.33
(b) 3
(c) 1.66
(d) 1.5

Answer: B

Question. The diameter of aperture of a plano-convex lens is 6 cm and its maximum thickness is 3 mm. If the velocity of light in the material of the lens is 2 × 10⁸ m/s, its focal length is
(a) 30 cm
(b) 60 cm
(c) 15 cm
(d) 10 cm

Answer: A

Question. A concave lens of focal length f produces an image (1/x) of the size of the object. The distance of the object from the lens is
(a) (x – 1) f
(b) (x + 1)f
(c) {(x – 1)/x}f
(d) {(x + 1)/x}f

Answer: A

Question. In case of displacement method of lenses, the product of magnification in both cases is
(a) 1
(b) 2
(c) Zero
(d) Infinite

Answer: A

Question. A person can see clearly only up to a distance of 25 cm. He wants to read a book placed at a distance of 50 cm. What kind of lens does he require for this purpose and what must be its power?
(a) Concave, – 2.0 D
(b) Convex, + 2.0 D
(c) Concave, – 1.0 D
(d) Convex, + 1.5 D

Answer: A

Question. An astronomical telescope has an objective of focal length 100 cm and an eye piece of focal length 5 cm. The final image of a star is seen 25 cm from the eyepiece. The magnifying power of the telescope is
(a) 24
(b) 26
(c) 22
(d) 20

Answer: A

Question. When a telescope is adjusted for normal vision, the distance of the objective from the eye-piece is found to be 80 cm. The magnifying power of the telescope is 19. What are the focal lengths of the lenses?
(a) 76 cm, 4 cm
(b) 50 cm, 30 cm
(c) 40 cm, 40 cm
(d) 61 cm, 19 cm

Answer: A

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

Answer: A

Question. A convex lens forms a real image of a point object at a distance of 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. The focal length of the concave lens is
(a) 40 cm
(b) 25 cm
(c) 20 cm
(d) 50 cm

Answer: A

Question. A convex lens of focal length 100 cm and a concave lens of focal length 10 cm are placed coaxially at a separation of 90 cm. If a parallel beam of light is incident on convex lens, then after passing through the two lenses the beam 
(a) Remains parallel
(b) Disappears
(c) Diverges
(d) Converges

Answer: A

Question. A driving mirror consists of a cylindrical mirror of radius of curvature 10 cm and the length over the curved surface is 10 cm. If the eye of the driver be assumed to be at a great distance from the mirror, then field of view in radian is
(a) 2.0
(b) 4.0
(c) 3.0
(d) 5.0

Answer: A

Question. In optical fibre, refractive index of inner part is 1.68 and refractive index of outer part is 1.44. The numerical aperture of the fibre is
(a) 0.8653
(b) 0.7653
(c) 0.6653
(d) 0.5653

Answer: A

Question. Compare the dispersive powers of two prisms if one of them deviates the blue and red rays through 10° and 6° respectively and the second prism through 8° and 4.5°
(a) 0.89
(b) 0.99
(c) 0.79
(d) 0.69

Answer: A

Question. A thin prism of angle 6° made of glass of refractive index 1.5 is combined with another prism made of glass of refractive index 1.75 to produce dispersion without deviation. Then the angle of the second prism is
(a) 4°
(b) 9°
(c) 5°
(d) 7°

Answer: A

Question. In a medium of refractive index 1.6 and having a convex surface has a point object in it at a distance of 12 cm from the pole. The radius of curvature is 6 cm. Locate the image as seen from air
(a) A virtual image at 30 cm
(b) A virtual image at 4.28 cm
(c) A real image at 30 cm
(d) A real image at 4.28 cm

Answer: A

Question. A point object is situated at a distance of 36 cm from the centre of the sphere of radius 12 cm and refractive index 1.5. Locate the position of the image due to refraction through sphere
(a) Both
(b) 36 cm from the centre
(c) 24 cm from the surface
(d) 24 cm from the centre

Answer: A

Question. A denser medium of refractive index 1.5 has a concave surface of radius of curvature 12 cm. An object is situated in the denser medium at a distance of 9 cm from the pole. Locate the image due to refraction in air.
(a) A virtual image at 4.8 cm
(b) A virtual image at 8 cm
(c) A real image at 8 cm
(d) A real image at 4.8 cm

Answer: A

Question. A light ray is travelling from air to glass. The reflected and refracted rays are perpendicular to each other. If the angle of incidence in air is i the refractive index of glass is
(a) tan i
(b) cot i
(c) cos i
(d) sin i

Answer: A