Ray Optics and Optical Instruments — DPP 2

20 NEET questions from Ray Optics and Optical Instruments, with answers and explanations. Attempt it as a timed test to get scoring, accuracy breakdown and mistake tracking.

Attempt this test free 20 questions · 30 minutes · +80 marks
1
Critical angle of light passing from glass to air is minimum for
  1. A Red
  2. B Green
  3. C Yellow
  4. D Violet
Show answer & explanation

Correct answer: D

$\sin \theta_{c}=\frac{1}{\mu} \& \mu \propto \frac{1}{\lambda}$
2
Brilliance of diamond is due to
  1. A Shape
  2. B Cutting
  3. C Reflection
  4. D T.I.R.
Show answer

Correct answer: D

3
Three prisms 1,2 and 3 have the prism angle $\mathrm { A } = 60 ^ { \circ }$, but their refractive indices are respectively 1.4, 1.5 and 1.6. If $\delta _ { 1 } , \delta _ { 2 } , \delta _ { 3 }$, be their respective angles of deviation then :-
  1. A $\delta _ { 3 } > \delta _ { 2 } > \delta _ { 1 }$
  2. B $\delta _ { 1 } > \delta _ { 2 } > \delta _ { 3 }$
  3. C $\delta _ { 1 } = \delta _ { 2 } = \delta _ { 3 }$
  4. D $\delta _ { 2 } > \delta _ { 1 } > \delta _ { 3 }$
Show answer & explanation

Correct answer: A

$\mu=\frac{\sin \left(\frac{A+\delta_{m}}{2}\right)}{\operatorname{Sin} \frac{A}{2}}$
A is same for all prism
Here $\mu_{1}<\mu_{2}<\mu_{3}$
∴ $\delta_{1}<\delta_{2}<\delta_{3}$
4
A boy stands straight infront of a mirror at a distance of 30 cm away from it. He sees his erect image whose height is $1 / 5 ^ { \text {th } }$ of his real height. The mirror he is using is -
  1. A Plane mirror
  2. B Convex mirror
  3. C Concave mirror
  4. D None
Show answer & explanation

Correct answer: B

Erect diminished image formed by convex mirror.
5
Which of the following is used in optical fibres
  1. A T.I.R.
  2. B Scattering
  3. C Diffraction
  4. D Refraction
Show answer

Correct answer: A

6
A point source of light is place 4 m below the surface of water of refractive index 5/3. The minimum diameter of a disc which should be placed over the source on the surface of water to cut-off all light coming out of water is.
  1. A 2 m
  2. B 6 m
  3. C 4 m
  4. D 3 m
Show answer & explanation

Correct answer: B

$\mathrm{r}=\frac{\mathrm{h}}{\sqrt{\mu_{\mathrm{w}}^{2}-1}}=\frac{4}{\sqrt{\left(\frac{5}{3}\right)^{2}-1}}=3 \mathrm{~m}$
Diameter of disc = 6 m
7
A ray falls on a prism ABC (AB = BC) and travels as shown in the figure. The minimum refractive index of the prism material should be
Ray Optics and Optical Instruments – NEET-20869
  1. A $\frac { 4 } { 3 }$
  2. B $\sqrt { 2 }$
  3. C 1.5
  4. D $\sqrt { 3 }$
Show answer & explanation

Correct answer: B

$\begin{array}{l}\sin \theta_{c}=\frac{1}{\mu} ; \sin 45^{\circ}=\frac{1}{\mu} \\ \mu=\sqrt{2}\end{array}$
8
An object is immersed in a fluid. In order that the object becomes invisible, it should.
  1. A Bahave as a perfect reflector
  2. B Absorb all light falling on it
  3. C Have refractive index one
  4. D Have refractive index exactly matching with that of the surrounding fluid
Show answer & explanation

Correct answer: D

If object will be invisible then R.I. of material and R.I. of medium should be same.
9
White light is incident on the interface of glass and air as shown in the figure. If green light is just totally internally reflected then the emerging ray in air contains
Ray Optics and Optical Instruments – NEET-20854
  1. A Yellow, orange, red
  2. B Violet, indigo, blue
  3. C All colours
  4. D All colours except green
Show answer & explanation

Correct answer: A

Ray Optics and Optical Instruments – NEET-20854
10
'Mirage' is a phenomenon due to
  1. A Reflection of light
  2. B Refraction of light
  3. C T.I.R. of light
  4. D Diffraction of light
Show answer

Correct answer: C

11
The angle of minimum deviation measured with a prism is $30 ^ { \circ }$ and the angle of prism is $60 ^ { \circ }$. The refractive index of prism material is -
  1. A $\sqrt { 2 }$
  2. B 2
  3. C $\frac { 3 } { 2 }$
  4. D $\frac { 4 } { 3 }$
Show answer & explanation

Correct answer: A

$\begin{array}{l}\mu=\frac{\sin \left(\frac{\delta_{\mathrm{m}}+\mathrm{A}}{2}\right)}{\sin \frac{\mathrm{A}}{2}} ; \mu=\frac{\sin \left(\frac{30^{\circ}+60^{\circ}}{2}\right)}{\sin \frac{60^{\circ}}{2}} ; \\ \frac{\sin 45^{\circ}}{\sin 30^{\circ}}=\frac{1}{\sqrt{2}} \times 2 ; \mu=\sqrt{2}\end{array}$
12
A ray of light travelling in air have wavelength λ, frequency n , velocity V and intensity I. If this ray enters into water than these parameters are $\lambda ^ { \prime } , \mathrm { n } ^ { \prime } , \mathrm { v } ^ { \prime }$ and $\mathrm { I } ^ { \prime }$ respectively. Which relation is correct from following-
  1. A $\lambda = \lambda ^ { \prime }$
  2. B $n = n$ '
  3. C $v = v ^ { \prime }$
  4. D $I = I ^ { \prime }$
Show answer & explanation

Correct answer: B

Frequency doesn't change with a change in medium
13
A point object O is placed in front of a glass rod having spherical end of radius of curvature 30 cm. The image formed would be
Ray Optics and Optical Instruments – NEET-20873
  1. A 30 cm left
  2. B infinity
  3. C 1 cm to the right
  4. D 18 cm to the left
Show answer & explanation

Correct answer: A

$\frac{\mu_{2}}{v}-\frac{\mu_{1}}{u}=\frac{\mu_{2}-\mu_{1}}{R} \Rightarrow \frac{1.5}{v}-\frac{1}{-15}=\frac{1.5-1}{30}$
v = –30 cm
14
An object is lying at a distance of 90 cm from a concave mirror of focal length 30 cm . The position and nature of image formed by it will be
  1. A 45 cm , of the size of object
  2. B 90 cm , smaller than object
  3. C 30 cm , bigger than object
  4. D -45 cm smaller than object
Show answer & explanation

Correct answer: D

Ray Optics and Optical Instruments – NEET-20837
15
The wavelength of light in two liquids 'x' and 'y' is $3500 \AA$ and $7000 \AA$, then the critical angle will be
  1. A $60 ^ { \circ }$
  2. B $45 ^ { \circ }$
  3. C $30 ^ { \circ }$
  4. D $15 ^ { \circ }$
Show answer & explanation

Correct answer: C

$\begin{array}{l}\sin \theta_{\mathrm{C}}=\frac{1}{{ }_{\mathrm{R}} \mu_{\mathrm{D}}} ; \quad\left[\because \mu \propto \frac{1}{\lambda}\right] \\ \sin \theta_{\mathrm{C}}=\frac{\lambda_{\mathrm{D}}}{\lambda_{\mathrm{R}}}=\frac{3500 \AA}{7000 \AA} ; \sin \theta_{\mathrm{C}}=\frac{1}{2} ; \theta_{\mathrm{C}}=30^{\circ}\end{array}$
16
A ray of light passes through equilateral Prism (μ = 1.5) such that angle of incidence is equal to angle of emergence and the later is equal to 3/4th of Prism angle. The angle of deviation is
  1. A $60^{\circ}$
  2. B $30^{\circ}$
  3. C $45^{\circ}$
  4. D $120^{\circ}$
Show answer & explanation

Correct answer: B

$\begin{array}{l}\delta_{m}=2 i-A \\ e=i=\frac{3}{4} \times 60^{\circ} \Rightarrow i=45^{\circ} \\ \delta_{m}=2 \times 45^{\circ}-60^{\circ} \\ \delta_{m}=30^{\circ}\end{array}$
17
A concave mirror gives an image three times as large as the object placed at a distance of 20 cm from it. For the image to be real, the focal length should be -
  1. A -10 cm
  2. B -15 cm
  3. C -20 cm
  4. D -30 cm
Show answer & explanation

Correct answer: B

$m=\frac{f}{f-u}$
Image to be real and three times m = –3
$-3=\frac{f}{f-(-20)}$
f = –15 cm
18
A microscope is focused on a mark, then a glass slab of refractive index 1.5 and thickness of 6 cm is placed on the mark to get the mark again in focus, the microscope should be moved
  1. A 4 cm
  2. B 2 cm
  3. C 6 cm
  4. D 8 cm
Show answer & explanation

Correct answer: B

Shifting $=t\left(1-\frac{1}{\mu}\right)=6\left(1-\frac{1}{1.5}\right)$
Shifting = 2 cm
19
When a ray of light enters a medium of refractive index μ, it is observed that the angle of refraction is half of the angle of incidence is than angle of incidence is
  1. A $2 \cos ^ { - 1 } ( \mu / 2 )$
  2. B $\cos ^ { - 1 } ( \mu / 2 )$
  3. C $2 \cos ^ { - 1 } ( \mu )$
  4. D $2 \sin ^ { - 1 } ( \mu / 2 )$
Show answer & explanation

Correct answer: A

Ray Optics and Optical Instruments – NEET-20853
20
The refractive index of the material of a prism is $\sqrt { 2 }$ and its refracting angle is $30 ^ { \circ }$. One of the refracting surfaces of the prism is silvered. A beam of monochromatic light entering the prism from the other face will retrace its path after reflection from the silvered surface if its angle of incidence on the prism is :-
  1. A $60 ^ { \circ }$
  2. B $0 ^ { \circ }$
  3. C $30 ^ { \circ }$
  4. D $45 ^ { \circ }$
Show answer & explanation

Correct answer: D

Ray Optics and Optical Instruments – NEET-20872 Light should be incident ⊥ on silvered surface
sin i = μ sin r
sin i = √2 sin 30
$i=\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)=45^{\circ}$

Attempt this as a timed test

Reading answers is not the same as sitting the paper. Attempt it timed and you get your score, per-question timing, and the mistakes tracked for revision.

Start free

More Ray Optics and Optical Instruments tests

Ray Optics and Optical Instruments — DPP 1 20 Q Ray Optics and Optical Instruments — DPP 3 20 Q
All Ray Optics and Optical Instruments tests →