Ray Optics NEET Questions with Solutions

Q: How many questions come from Ray Optics in NEET 2027?

You can expect 2 to 3 questions in NEET 2027. The chapter has high PYQ frequency. Common asks: image formation by spherical mirrors and thin lenses, lens-maker formula, total internal reflection, prism deviation and angular dispersion, and microscope or telescope magnification.

Q: What is the Cartesian sign convention?

All distances are measured from the pole of the mirror or optical centre of the lens, along the principal axis. Distances measured in the direction of incident light (usually rightwards) are positive, and against it are negative. Heights above the principal axis are positive, below are negative. Focal length of a concave mirror or convex lens (used as converging) is negative or positive depending on convention. Apply consistently and you will not be confused.

Q: What does the mirror formula tell you?

1 over v plus 1 over u equals 1 over f. With sign convention: real object u is negative, real image v is negative for a concave mirror. Magnification m equals minus v over u. Positive m means erect image, negative m means inverted. |m| > 1 means magnified, |m| < 1 means diminished.

Q: What is Snell's law?

When light passes from medium 1 to medium 2, n_1 sin theta_1 equals n_2 sin theta_2. The angles are measured from the normal. Light bends towards the normal when going from rarer to denser (n increases) and away from the normal when going denser to rarer.

Q: When does total internal reflection happen?

Only when light goes from a denser medium to a rarer medium. The critical angle is sin theta_c equals 1 over n where n is the refractive index of the denser medium relative to the rarer. For glass-air, theta_c ≈ 42°. Light at angles greater than theta_c is totally reflected. Used in optical fibres, prismatic binoculars and brilliance of diamonds.

Q: What is the lens-maker formula?

1 over f equals (n - 1)(1 over R_1 minus 1 over R_2). Here n is the refractive index of the lens material, R_1 is the radius of the surface light hits first and R_2 is the second surface. Use Cartesian convention. For a biconvex lens with both R equal, 1 over f equals 2(n - 1) over R.

Q: How do you combine two thin lenses?

In contact: 1 over f equals 1 over f_1 plus 1 over f_2 (or P equals P_1 plus P_2 in diopters). For lenses separated by distance d: 1 over f equals 1 over f_1 plus 1 over f_2 minus d over (f_1 f_2).

Q: What is the formula for minimum deviation in a prism?

At minimum deviation, the ray inside the prism travels parallel to the base, so r_1 = r_2 = A over 2 and i_1 = i_2 = (A + delta_m) over 2. Refractive index n equals sin((A + delta_m) / 2) divided by sin(A / 2). For small prism angles, delta = (n - 1) A.

Q: What is the difference between angular dispersion and dispersive power?

Angular dispersion equals (n_v - n_r) A or delta_v - delta_r: the spread of colours in radians. Dispersive power equals (n_v - n_r) divided by (n_y - 1) where n_y is the refractive index for yellow (mean): a dimensionless property of the material. Dispersive power of crown glass is around 0.02; of flint glass around 0.03.

Q: What is the magnification of a compound microscope and an astronomical telescope?

Compound microscope: M = (L / f_o)(D / f_e) for image at near point, where L is tube length, f_o is objective focal length, f_e is eyepiece focal length, D = 25 cm. Astronomical telescope (normal adjustment, image at infinity): M = f_o / f_e and length L = f_o + f_e. For maximum magnification, use a long-focal-length objective and a short-focal-length eyepiece.

Question 1

A concave mirror has f = -10 cm. Object at u = -30 cm. Image at:

Accepted Answer

-15 cm

Question 2

Convex mirror image is always:

Accepted Answer

Virtual, erect, diminished

Question 3

Light goes from air (n = 1) to glass (n = 1.5) at θ_1 = 30°. Find θ_2.

Accepted Answer

19.5°

Question 4

Critical angle for glass-air interface (n = 1.5):

Accepted Answer

42°

Question 5

Coin in water at 8 cm real depth. Apparent depth (n = 1.33):

Accepted Answer

6 cm

Question 6

Convex lens f = +20 cm. Object u = -30 cm. Image v:

Accepted Answer

+60 cm

Question 7

Biconvex lens, n = 1.5, |R_1| = |R_2| = 20 cm. f =

Accepted Answer

+20 cm

Question 8

Small-angle prism, A = 6°, n = 1.5. Deviation δ:

Accepted Answer

3°

Question 9

Astronomical telescope, f_o = 100 cm, f_e = 5 cm. Magnification (normal adj):

Accepted Answer

20×

Question 10

Convex lens f = 10 cm. Object placed at u = -10 cm. Image at:

Accepted Answer

Infinity

Question 11

Object at C (= 2f) of concave mirror. Image:

Accepted Answer

At C, same size, inverted, real

Question 12

Light incident from glass (n = 1.5) to water (n = 1.33). Critical angle:

Accepted Answer

62.5°

Question 13

Two thin lenses in contact: f_1 = +20 cm, f_2 = -30 cm. Equivalent f:

Accepted Answer

+60 cm

Question 14

Prism A = 60°, δ_m = 30°. Refractive index:

Accepted Answer

√2

Question 15

Compound microscope: f_o = 1 cm, f_e = 5 cm, L = 16 cm. Magnification (image at D):

Accepted Answer

96×

Question 16

Real image of an object placed at 30 cm from a concave mirror is formed at 60 cm. Focal length:

Accepted Answer

-20 cm

Question 17

Real depth = 4 cm, apparent depth = 3 cm. n =

Accepted Answer

4/3

Question 18

Power of a convex lens of f = 25 cm:

Accepted Answer

+4 D

Question 19

Optical fibre transmits light by:

Accepted Answer

TIR

Question 20

When light goes from rarer to denser, what increases?

Accepted Answer

Refractive index of the medium relative to first

Question 21

A glass lens (n = 1.5) of focal length f in air. When immersed in water (n = 1.33), focal length:

Accepted Answer

Becomes 4f

Question 22

Magnification of a concave mirror is +2 (object inside F). Then:

Accepted Answer

Virtual, erect, magnified 2×

Question 23

Dispersive power of a prism is given by:

Accepted Answer

[math]

Question 24

In normal adjustment, length of an astronomical telescope is:

Accepted Answer

f_o + f_e

Question 25

A diamond (n = 2.42) has critical angle:

Accepted Answer

24.4°

Question 26

Magnifying power of a simple microscope (image at near point):

Accepted Answer

1 + D/f

Question 27

Two lenses of P_1 = +5 D and P_2 = -3 D in contact. Combined power:

Accepted Answer

+2 D

Question 28

Speed of light in glass (n = 1.5):

Accepted Answer

[math] m/s

Question 29

A glass slab of thickness 6 cm and n = 1.5 placed on text. Apparent shift of text:

Accepted Answer

2 cm

Question 30

Object placed at u = -10 cm in front of a convex mirror f = +15 cm. Image v:

Accepted Answer

+6 cm

Question 31

Image of an object at u = -20 cm by lens of P = +5 D:

Accepted Answer

Infinity

Question 32

To get high resolving power of a microscope, one should:

Accepted Answer

Decrease λ

Ray Optics and Optical InstrumentsNEET Physics · Class 12 · NCERT Chapter 9

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Ray Optics and Optical InstrumentsNEET Physics · Class 12 · NCERT Chapter 9

1NEET 2018EasyA concave mirror has f = -10 cm. Object at u = -30 cm. Image at:

2NEET 2019EasyConvex mirror image is always:

3NEET 2020EasyLight goes from air (n = 1) to glass (n = 1.5) at θ_1 = 30°. Find θ_2.

4NEET 2021EasyCritical angle for glass-air interface (n = 1.5):

5NEET 2022EasyCoin in water at 8 cm real depth. Apparent depth (n = 1.33):

6NEET 2023EasyConvex lens f = +20 cm. Object u = -30 cm. Image v:

7NEET 2024MediumBiconvex lens, n = 1.5, |R_1| = |R_2| = 20 cm. f =

8NEET 2017MediumSmall-angle prism, A = 6°, n = 1.5. Deviation δ:

9NEET 2018MediumAstronomical telescope, f_o = 100 cm, f_e = 5 cm. Magnification (normal adj):

10NEET 2019MediumConvex lens f = 10 cm. Object placed at u = -10 cm. Image at:

11NEET 2020MediumObject at C (= 2f) of concave mirror. Image:

12NEET 2021MediumLight incident from glass (n = 1.5) to water (n = 1.33). Critical angle:

13NEET 2022MediumTwo thin lenses in contact: f_1 = +20 cm, f_2 = -30 cm. Equivalent f:

14NEET 2023MediumPrism A = 60°, δ_m = 30°. Refractive index:

15NEET 2024MediumCompound microscope: f_o = 1 cm, f_e = 5 cm, L = 16 cm. Magnification (image at D):

16NEET 2017MediumReal image of an object placed at 30 cm from a concave mirror is formed at 60 cm. Focal length:

17NEET 2018MediumReal depth = 4 cm, apparent depth = 3 cm. n =

18NEET 2019MediumPower of a convex lens of f = 25 cm:

19NEET 2020MediumOptical fibre transmits light by:

20NEET 2021MediumWhen light goes from rarer to denser, what increases?

21NEET 2022MediumA glass lens (n = 1.5) of focal length f in air. When immersed in water (n = 1.33), focal length:

22NEET 2023MediumMagnification of a concave mirror is +2 (object inside F). Then:

23NEET 2024MediumDispersive power of a prism is given by:

24NEET 2017MediumIn normal adjustment, length of an astronomical telescope is:

25NEET 2018MediumA diamond (n = 2.42) has critical angle:

26NEET 2019MediumMagnifying power of a simple microscope (image at near point):

27NEET 2020MediumTwo lenses of P_1 = +5 D and P_2 = -3 D in contact. Combined power:

28NEET 2021MediumSpeed of light in glass (n = 1.5):

29NEET 2022MediumA glass slab of thickness 6 cm and n = 1.5 placed on text. Apparent shift of text:

30NEET 2023MediumObject placed at u = -10 cm in front of a convex mirror f = +15 cm. Image v:

31NEET 2024MediumImage of an object at u = -20 cm by lens of P = +5 D:

32NEET 2017MediumTo get high resolving power of a microscope, one should:

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