Contents

## NEET Physics Chapter Wise Mock Test – Optics

Question 1:

Sun is visible a little before the actual sunrise and until a little after the actual sunset. This is due to

(a) total internal reflection

(b) reflection

(c) refraction

(d) polarisation

Question 2:

The magnification of a compound microscope is 30 and the focal length of its eye piece is 5cm. The magnification produced by the objective, when the image is to be formed at least distance of distinct vision (25 cm), is

(a) 5

(b) 6

(c) 8

(d) 10

Question 3:

A simple microscope consists of a concave lens of power -10 D and a convex lens of power +20 D in contact.

If the image is formed at infinity, then the magnifying power (D = 25 cm) is

(a) 2.5

(b) 3.5

(c) 2.0

(d) 3.0

Question 4:

Interference is possible in

(a) light waves only

(b) sound waves only

(c) both light and sound waves

(d) neither light nor sound waves

Question 5:

The axes of the polariser and analyser are inclined to each other at 45°. If the amplitude of the unpolarised light incident on the polariser is a, then what is the amplitude of the light transmitted through the analyser?

(a) a/2

(b) a/√2

(c) (√3 a)/2

(d) 3a/4

Question 6:

A ray is incident at an angle of incidence i on one surface of a prism of small angle A and emerge normally from opposite surface. If the refractive index of the material of prism is μ, the angle of incidence i is nearly equal to

(a) A/μ

(b) A/2μ

(c) μA

(d) μA/2

Question 7:

A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5. The wavelength of refracted light will be

(a) dependent on intensity of refracted light

(b) same

(c) smaller

(d) larger

Question 8:

There is a prism with refractive index equal to 42 and the refracting angle equal to 30°. One of the refracting

surface of the prism is polished. A beam of monochromatic will retrace its path is its angle of incidence over the refracting surface of the prism is

(a) 0°

(b) 30°

(c) 45°

(d) 60°

Question 9:

What is Brewster angle for air to glass transition? (μ of glass is 1.5)

(a) 56.3°

(b) 57.5°

(c) 59.1°

(d) 83°

Question 10:

In a double slit experiment 5^{th} dark fringe is formed opposite to one of the slits. The wavelength of light is

(a) d^{2}/6D

(b) d^{2}/5D

(c) d^{2}/15D

(d) d^{2}/9D

Question 11:

Question 12:

The illuminance of a surface 2m away from a point source is 4 Wm^{-2}. It will be 2 Wm^{-2} when the distance

of the point from the source is

(a) 2√2 m

(b) 2/√2 m

(c) √2 m

(d) 1/√2 m

Question 13:

A wavefront is represented by the plane y = 3 – x. The propagation wave takes place at

(a) 45° with the +ve x -direction

(b) 135° with the +vex-direction

(c) 60° with the +vex-direction

(d) no sufficient data

Question 14:

In Young’s double slit experiment with monochromatic light of wavelength 600nm, the distance between slits is 10^{-3}m. For changing fringe width by 3 x 10^{-5} m

(a) the screen is moved away from the slits by 5 cm

(b) the screen is moved by 5 cm towards the slits

(c) the screen is moved by 3 cm towards the slits

(d) Both (a) and (b) be correct

Question 15:

Question 16:

A convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together. What will be their resulting power?

(a) +6.5 D

(b) -6.5 D

(c) +7.5D

(d) -0.75D

Question 17:

Unpolarised light of intensity 32 Wm^{-2} is incident on the combination of three polaroids. The first and last

polaroids are crossed. If the intensity of the light transmitted through the combination be 3 Wm^{-2}, then

what is the angle between the transmission axes of first two polaroids?

(a) 0°

(b) 30°

(c) 45°

(d) 60°

Question 18:

Two lamps of powers P_{1} and P_{2} are placed on either side of a paper having an oil spot. The lamps are at

1m and 2m respectively, on either side of the paper and the oil spot is invisible. What is the value of P_{1}/P_{2} ?

(a) 0.25

(b) 0.40

(c) 0.50

(d) 0.60

Question 19:

An astronomical telescope of ten-fold angular magnification has a length of 44 cm. The focal length of the

objective is

(a) 440cm

(b) 44cm

(c) 40cm

(d) 4cm

Question 20:

The wavefront due to a source situated at infinity is

(a) spherical

(b) cylindrical

(c) planar

(d) None of these

Question 21:

The refractive index of the material of the prism is √3, then the angle of minimum deviation of the prism is

(a) 30°

(b) 45°

(c) 60°

(d) 75°

Question 22:

A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre

of the screen . Find the width of the slit.

(a) 0.2 mm

(b) 1.0mm

(c) 4.1 mm

(d) 0.6 mm

Question 23:

A transparent cube contains small air bubble. Its apparent distance is 2cm when seen through one face and 5 cm when seen through other face. If the refractive index of the material of the cube is 1.5, the real length of the

edge of cube must be

(a) 7 cm

(b) 7.5 cm

(c) 10.5 cm

(d) 14/3 cm

Question 24:

Transmission of light in optical fibre is due to

(a) scattering

(b) diffraction

(c) polarisation

(d) multiple total internal reflections

Question 25:

Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them,

which are situated at a distance of 50 m from eye? (The wavelength of light is 500Å)

(a) 2.32 m

(b) 4.28 mm

(c) 1.25 cm

(d) 12.48 cm

Question 26:

Two nicol prisms are placed with their principal planes at 60°. What percentage of light incident on the combination is transmitted?

(a) 75%

(b) 60%

(c) 25%

(d) 12.5%

Question 27:

In Young’s double slit experiment, if the slit widths are in the ratio 1:9, the ratio of the intensity at minima to that at maxima will be

(a) 1

(b) 1/9

(c) 1/4

(d) 1/3

Question 28:

Two coherent light sources S_{1} and S_{2} (λ= 6000Å) are 1 mm apart from each other. The screen is placed at a distance of 25 cm from the sources. The width of the fringes on the screen should be

(a) 0.015 cm

(b) 0.025 cm

(c) 0.010 cm

(d) 0.030 cm

Question 29:

Light from two coherent sources of same amplitude (A) and wavelength (Å) illuminates the screen. The intensity of central maximum is I_{0}. If the source were incoherent, the intensity at the same point will be

(a) I_{0}/2

(b) I_{0}

(c) 2I_{0}

(d) 4I_{0}

Question 30:

What will be the angle of diffraction for the first minimum due to Fraunhoffer diffraction with sources of light of wavelength 550nm and slit of width 0.55 mm?

(a) 1 rad

(b) 0.1 rad

(c) 0.01 rad

(d) 0.001 rad

Question 31:

Young’s double slit experiment is performed with light of wavelength 550 nm. The separation between the slits is 1.10 mm and the screen is placed at a distance of 1m. What is the distance between the consecutive bright

and dark fringes ?

(a) 0.5 mm

(b) 1.0 mm

(c) 1.5 mm

(d) None of these

Question 32:

To produce an achromatic combination a convex lens of focal length 42 cm and dispersive power 0.14 is placed in contact with a concave lens of dispersive power 0.21. The focal length of the concave lens is

(a) 21 cm

(b) 42 cm

(c) 63 cm

(d) 84 cm

Question 33:

The focal length of a lens for red and violet colours are 16.4 cm and 16 cm. What is its dispersive power?

(a) 0.050

(b) 0.025

(c) 0.012

(d) 0.006

Question 34:

The luminous flux from a 100W electric lamp is 6830 lumen. What is the efficiency of the lamp?

(a) 1%

(b) 5%

(c) 10%

(d) 50%

Question 35:

The luminous efficiency of the lamp is 5 Im W^{-1}. If the luminous intensity of the lamp be 35 Cd, then power of the lamp is

(a) 28 W

(b) 88 W

(c) 112W

(d) 140W

Direction (Q.NOs. 36-40): In each of the following questions a statement of Assertion is given followed by a corresponding statement of Reason just below it. Of the statements mark the correct answer as :

(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion

(b) If both Assertion and Reason are true but the Reason is not correct explanation of the Assertion .

(c) If Assertion is true but Reason is false

(d) If both Assertion and Reason are false

Question 36:

Assertion (A): The resolving power of a telescope is more, if the diameter of the objective lens is more.

Reason (R): Objective lens of large diameter collects more light.

Question 37:

Assertion (A): The focal length of the objective of the telescope is larger than that of eyepiece.

Reason (R): The resolving power of telescope increase? when the aperture of objective is small.

Question 38:

Assertion (A): Convergent lens property of converging remain same in all mediums.

Reason (R): Property of lens whether the ray is diverging or converging is independent of the surrounding

medium.

Question 39:

Assertion (A): If Brewster’s angle be 6, then critical angle is sin^{-1}(cotθ).

Reason (R): The refractive index of medium μ=1/SinC , C being critical angle.

Question 40:

Assertion (A): In Young’s double slit experiment interference pattern disappear when one of the slits is closed.

Reason (R): Interference occurs due to superimposition of light waves from two coherent sources.

Question 41:

A ray of light passes through an equilateral prism, such that an angle of incidence is equal to the angle of emergence and the latter is equal to 3/4 th the angle of prism. The angle of deviation is

(a) 45°

(b) 39°

(c) 20°

(d) 30°

Question 42:

One face AC of the glass prism is silvered as shown and the principle section of the glass prism is an isosceles triangle ABC with AB = AC. The ∠BAC, if the ray incident normally on the face AB and after two reflections, it emerges from the base BC, perpendicular to it, is

(a) 70°

(b) 36°

(c) 72°

(d) 44°

Question 43:

A man having height 6 m, observes image of 2m height erect, then mirror used is

(a) concave

(b) convex

(c) plane

(d) None of these

Question 44:

A vessel consists of two plane mirrors at right angle (as shown in the figure). The vessel is filled with water.

The total deviation in incident ray is

(a) 0°

(b) 90°

(c) 180°

(d) None of these

Question 45:

An object is placed at a distance equal to focal length of convex mirror. If the focal length of the mirror be f,

then the distance of the image from the pole of the mirror is

(a) less than f

(b) equal to f

(c) more than f

(d) infinity

Question 46:

If a ray light is incident on an equilateral glass prism PQR placed on a horizontal table, then for the minimum deviation which of the following is true?

(a) AB is horizontal

(b) CD is horizontal

(c) Either AB or CD is horizontal

(d) BC is horizontal

Question 47:

Question 48:

If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together,

what will be their resultant power? .

(a) +0.65D

(b) -0.65D

(c) +0.75D

(d) -0.75D

Question 49:

A convex lens forms a full image of the object an a screen. If half of the lens is covered with an opaque object,

then

(a) the image disappears

(b) half of the image is seen

(c) full image is seen and of same intensity

(d) full image is seen and of decreased intensity

Question 50:

What is the focal length of a convex-lens of focal length 30 cm in contact with a concave lens of focal

length 20 cm. Is the system a converging or a diverging lens? Ignore thickness of the lenses.

(a) 60 cm, diverging

(b) 40 cm, converging

(c) 50 cm, converging

(d) 40 cm, diverging

### Answers:

### Hints And Solutions: