Ray Optics · JEE Main previous year questions

2020 14 questions

1. Q382020 · 6 Sept 2020 · Shift 1

   A point like object is placed at a distance of 1 m in front of a convex lens of focal length 0.5 m. A plane mirror is placed at a distance of 2 m behind the lens. The position and nature of the final image formed by the system is :

   1. A.2.6 m from the mirror, real
   2. B.1 m from the mirror, real
   3. C.2.6 m from the mirror, virtual
   4. D.1 m from the mirror, virtual
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   Answer: A

2. Q302020 · 6 Sept 2020 · Shift 2

   A double convex lens has power P and same radii of curvature R of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power 1.5 P is :

   1. A.$\frac{R}{3}$
   2. B.$\frac{3R}{2}$
   3. C.$\frac{R}{2}$
   4. D.$2R$
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   Answer: A

3. Q502020 · 3 Sept 2020 · Shift 1· Numerical answer
   
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   Answer: 158

4. Q492020 · 3 Sept 2020 · Shift 2· Numerical answer

   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 from the mirror. If the object is moved with a speed of $9\mathrm{cm}{\mathrm{s}}^{-1}$, the speed (in $\mathrm{cm}{\mathrm{s}}^{-1}$) with which image moves at that instant is _______.

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   Answer: 1

5. Q412020 · 2 Sept 2020 · Shift 1
   
   1. A.Inverted, real and unmagnified
   2. B.Inverted, real and magnified
   3. C.Erect, virtual and magnified
   4. D.Erect, virtual and unmagnified
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   Answer: A

6. Q502020 · 2 Sept 2020 · Shift 2· Numerical answer

   A light ray enters a solid glass sphere of refractive index $\mu =\sqrt{3}$ at an angle of incidence $60^{\circ }$. The ray is both reflected and refracted at the farther surface of the sphere. The angle (in degrees) between the reflected and refracted rays at this surface is _______.

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   Answer: 90

7. Q352020 · 9 Jan 2020 · Shift 1

   A vessel of depth 2h is half filled with a liquid of refractive index $2\sqrt{2}$ and the upper half with another liquid of refractive index $\sqrt{2}$. The liquids are immiscible. The apparent depth of the inner surface of the bottom of vessel will be :

   1. A.$\frac{h}{\sqrt{2}}$
   2. B.$\frac{h}{3\sqrt{2}}$
   3. C.$\frac{3}{4}h\sqrt{2}$
   4. D.$\frac{h}{2(\sqrt{2}+1)}$
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   Answer: C

8. Q372020 · 9 Jan 2020 · Shift 1

   The aperture diameter of a telescope is 5m. The separation between the moon and the earth is $4\times 10^5\text{ km}$. With light of wavelength of $5500\text{ A˚}$, the minimum separation between objects on the surface of moon, so that they are just resolved, is close to :

   1. A.20 m
   2. B.200 m
   3. C.600 m
   4. D.60 m
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   Answer: D

9. Q352020 · 9 Jan 2020 · Shift 2

   There is a small source of light at some depth below the surface of water (refractive index = $\frac{4}{3}$) in a tank of large cross sectional surface area. Neglecting any reflection from the bottom and absorption by water, percentage of light that emerges out of surface is (nearly) : [Use the fact that surface area of a spherical cap of height h and radius of curvature r is $2\pi rh$]:

   1. A.17%
   2. B.34%
   3. C.50%
   4. D.21%
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   Answer: A

10. Q362020 · 8 Jan 2020 · Shift 1

    The magnifying power of a telescope with tube 60 cm is 5. What is the focal length of its eye piece ?

    1. A.40 cm
    2. B.10 cm
    3. C.30 cm
    4. D.20 cm
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    Answer: B

11. Q472020 · 8 Jan 2020 · Shift 1· Numerical answer

    A point object in air is in front of the curved surface of a plano-convex lens. The radius of curvature of the curved surface is 30 cm and the refractive index of the lens material is 1.5, then the focal length of the lens (in cm) is ______.

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    Answer: 60

12. Q432020 · 8 Jan 2020 · Shift 2
    
    1. A.
    2. B.
    3. C.
    4. D.
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    Answer: C

13. Q362020 · 7 Jan 2020 · Shift 1

    If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to :

    1. A.22 mm
    2. B.12 mm
    3. C.33 mm
    4. D.2 mm
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    Answer: A

14. Q352020 · 7 Jan 2020 · Shift 2

    A thin lens made of glass (refractive index = 1.5) of focal length f = 16 cm is immersed in a liquid of refractive index 1.42. If its focal length in liquid is $f_1$, then the ratio $\frac{f_1}{f}$ is closest to the integer :

    1. A.17
    2. B.1
    3. C.9
    4. D.5
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    Answer: C