Physics Optical Instruments MCQs Chapter 10 Class 11 - PLS Academy

Physics Optical Instruments for Entry Tests and FSC Exams

Physics Optical Instruments is an important chapter of First Year Physics and is frequently tested in MCQs-based examinations. It is especially relevant for MDCAT, NUMS, AKU, NUST, UET ECAT, and FSC board exams. This chapter focuses on key instruments such as the simple microscope, compound microscope, and astronomical telescope, along with concepts like magnifying power and resolving power. Many students prefer to download free MCQs and start free preparation for this topic due to its scoring nature.

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Created on February 07, 2022 By Ali Durrani

Physics Ch 10 Class 11 OPTICAL INSTRUMENTS

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1 / 66

What should the distance of an object from a convex lens of focal length f=10 cm in order to produce an erect image twice as large as the object?

NTS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 20 cm from the lens

B) 15 cm from the lens

C) 10 cm from the lens

D) 05 cm from the lens

2 / 66

The diameter of a lens is called

Focal length

Principal axis

Aperture

Radius of curvature

3 / 66

An astronomical telescope has Magnifying power 5. If the focal length is 20 cm then what is the focal length of the objective?

NUMS 2019 Cancelled
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

B) 0.1 m

C) 50 cm

D) 25 cm

E) 15 cm

4 / 66

The interference of green photon to red photon will cause:

PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Spectrum

B) Interference

C) Diffraction

D) No effect

5 / 66

Michelson measured the length of a standard meter in terms of the wavelength of:

PMC Practice 2
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Green cadmium light

B) Violet cadmium light

C) Red cadmium light

D) Blue cadmium light

6 / 66

Final image produced by a compound microscope is

Real and inverted

Real and erect

Virtual and erect

Virtual and inverted.

7 / 66

Laser beam can be used to generate three dimensional objects in a process called:

NUMS 2017
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Iconography

B) Holography

C) Logography

D) Photography

8 / 66

Bragg’s Law for measurement of wavelength à. of i-rays, using crystal lattice planes having distance d between each other, for constructive interference for integral multiple of i is.

NTS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) mλ = 2d/ sinθ

B) 2λ =md sinθ

C) mλ = 2d sinθ

D) dλ = 2m sinθ

9 / 66

A convex lens of focal length ‘f1’and a concave lens of focal length ‘f2’ are placed in contact. The focal
length of the combination is

f2 + f1

f2 – f1

f1f2/f2+f1

f1f2/f1-f2

10 / 66

Critical angle is that incident angle in denser medium for which angle of refraction is.

180

11 / 66

In Young’s Double slit experiment, if the spacing between the slit is doubled and the linear distance from the screen is reduced to one half then the spacing between the two adjacent bright fringes will be ____ of actual value.

NUMS 2017
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Remains same

B) Reduce to one half

C) Reduce to one quarter

D) Increase to twice

12 / 66

In Double Slit experiment, the fringe spacing of the diffracted rays increases when:

UHS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) the wavelength of the diffracted rays increases

B) the distance between the slits increases

C) the distance from mid points of the slits to the central of the fringe on the screen increases

D) the distance between the screen and the slits decreases

13 / 66

The least distance of distinct vision for normal eye is approximately

10 cm

15 cm

20 cm

25 cm

14 / 66

If a single convex lens is placed close to the eye, it can be used as a

telescope

simple microscope

compound microscope

refracting telescope

15 / 66

A point where the incident parallel rays of light converge or appear to diverge after passing through a lens
is called

(a) Center of curvature

Focus

Aperture

16 / 66

A lens, which is thicker at the center and thicker at the edges, is called.

Concave lens

Convex lens

Plano convex lens

Plano concave lens

17 / 66

In multimode step index fibre the refractive index of core and cladding is

Same

Different

Zero

Different with refractive index of core higher than cladding

18 / 66

A convex lens gives a virtual image only when the objects leis

Between principal focus and center of curvature

Beyond 2 f

At the principal focus

Between principal focus and optical center

19 / 66

In going form a denser to rarer medium a array of light is

undeviated

bent away form the normal

bent towards the normal

polarized

20 / 66

Dioptre power of an concave lens of 10 cm focal length is

10 dioptre

-10 dioptre

1/10 dioptre

-1/10 dioptre

21 / 66

The property of light, bending around obstacles and spreading of waves into the geometrical shadow of an obstacle is called ______.

NUMS 2019 Reconduct
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Shadow

B) Refraction

C) Diffraction

D) Reflection

22 / 66

If placed in contact, the focal length of the combination of two convex lenses of equal focal lengths f,
will be

zero

f/2

23 / 66

If d is the distance of distinct vision, the magnifying power of a magnifying glass of focal length f is

d/f

f/d

1 + d/f

1 + f/d

24 / 66

The least distance of distinct vision for a normal eye is

15cm

25cm

30cm

40cm

25 / 66

Monochromatic light means the light having:

NUMS 2018
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) One colour

B) Single frequency

C) Single wavelength

D) All of above

26 / 66

Two convex lenses of equal focal length ‘f’ are placed in contact, the resultant focal length of the
combination is

Zero

f/2

27 / 66

If a convex lens of focal length ‘f’ is cut into two identical halves along the lens diameter, the focal length
of each half is.

f/2

3f/2

28 / 66

Coherent source of light means?

PMC Practice 3
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Multiple wavelengths

B) Double wavelength

C) Single wavelength

D) Coherent photons

29 / 66

Dispersional effect may produced error in light signals. This type of error is minimum in.

Single mode step index fibre

Multimode step index fibre

Multimode graded index fibre

Monomode step index fibre

30 / 66

A double convex lens acts as a diverging lens when the object is placed

at the focus

at 2f

between f and 2f

within the focal length

31 / 66

A lens which converges a beam of parallel rays to a point is called

Diverging (or concave) lens

Converging (or convex) lens

Plano concave lens

Plano convex lens

32 / 66

Wave nature of light is proved by:

PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Polarisation

B) Black body radiation

C) Compton's effect

D) Photoelectric effect

33 / 66

If an object is placed away form ‘2f’ of a converging lens, then the image will be

Real and erect

Virtual and erect

Real and inverted

Virtual

34 / 66

The electrical signals change into light signals for transmission through optical fibre. A light pulse
represent.

Zero (0)

One (1)

Both zero (0) and one (1)

Neither zero (0) nor one (1)

35 / 66

A line normal to the wavefront, showing the direction of the propagation of light is called the:

PMC Practice 2
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Tangent

B) Radius

C) Wavelength

D) Ray of light

36 / 66

In a Young’s double-slit experiment, fringes are very close to each other. How can we increase the distance between fringes?

PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) By increasing the distance between light source and slits

B) By increasing the distance from slits to the screen

C) By increasing the distance between slits

D) By increasing the frequency of ligh

37 / 66

Spherical aberration can be reduced by using

double convex lens

central portion of the lens

edge portion of the lens

parallel rays

38 / 66

There is no noticeable boundary between core and cladding.

Multi mode step index fibre

Multi mode graded index fibre

Single mode step index fibre

All types of fibre

39 / 66

In a scanning electron microscope, image formed is:

PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 2D

B) 3D

C) 1D

D) Any of these

40 / 66

White light does not focus to a single point after passing through a convex lens due to

chromatic aberration

(b) spherical aberration

distortion

spherical and chromatic aberrations

41 / 66

The light exhibits the phenomena of constructive interference under the situation when it is ______ and ______.

NUMS 2018
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Monochromatic and in Phase

B) Monochromatic and out of Phase

C) In phase and non – monochromatic

D) Out of phase and non – monochromatic

42 / 66

In Young’s double-slit experiment, if d is the separation between two slits 1 is the wavelength of light and θ is the angle of the line from the centre of slits to the point of observation on the screen; then for maxima (bright fringe); the formula is _________.

NTS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 2d sinθ = mλ ; m = 0 .. 2, …

B) dsinθ = mλ ; m = 0, 1, 2, …

C) .sin θ = (m + ½) λ ; m = 0, 1, 2, …..

D) 2msinθ = dλ ; m = 0, 1, 2, ….

43 / 66

Image of an object 5 mm high is only 1 cm high. Magnification produced by lens is

0.5

0.2

44 / 66

The property of light, bending around obstacles and spreading of waves into the geometrical shadow of an obstacle is called ______.

NUMS 2019 Reconduct
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Shadow

B) Refraction

C) Diffraction

D) Reflection

45 / 66

In a double slit experiment, two slits are 0.2 mm apart with a screen at a distance of 1m. The third bright fringe is found to be displaced at a distance of 7.5 mm from the central fringe. What is the value of the wavelength?

NUMS 2019 Cancelled
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 0.03 mm

B) 0.004 mm

C) 0.00006 mm

D) 0.0005 mm

46 / 66

A convex and concave lens of focal length ‘f’ are in contact, the focal length of the combination will be.

Zero

f/2

Infinite

47 / 66

Which of the following particles has greater wavelengths having the same velocity?

NUMS 2019 Reconduct
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Proton

B) Neutron

C) Electron

D) Alpha particle

48 / 66

A spectrometer is used to find.

Wave length of light

Refractive index of the prism

Wavelength of different colours

None

49 / 66

If a convex lens of large aperture fails to converge the light rays incident on it to a single point, it is said to
suffer form

Chromatic aberration

Spherical aberration

Both spherical and chromatic

Distortion

50 / 66

Which one type of fibre is more suitable for transmission of signals in which white light is used?Which one type of fibre is more suitable for transmission of signals in which white light is used?

Mono mode step index fibre

Multi mode step index fibre

Multi mode graded index fibre

Single mode step index fibre

51 / 66

Lasers are used for producing an intense, ____ and coherent beam of visible light.

NUMS 2017
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Monochromatic

B) Bichromatic

C) Multichromatic

D) Non Chromatic

52 / 66

A diffraction grating has 500 lines per mm, its grating element d is equal to:

UHS 2018
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 2 x 10-6meter

B) 2 x 10-2meter

C) 2 x 10-2cm

D) 2 x 10-6cm

53 / 66

The film of oil on water shows colour pattern when illuminated by white light due to:

NUMS 2018
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) Interference

B) Dispersion

C) Polarization

D) Scattering

54 / 66

for normal adjustment, length of astronomical telescope is

fo + fe

fo – fe

fo/fe

fe/fo

55 / 66

least distance of distinct vision

increases with increase in age

decrease with increaser in age

neither increases nor decreases

d. becomes infinite after 60 years

56 / 66

The objective of a microscope is a lens of

large focal length and converging properties

moderate focal length and diverging properties

very short focal length and converging properties

moderate focal length and converging properties

57 / 66

Magnifying power of simple microscope

Increase with increase in focal length

Increase with decrease in focal length

No effect with decrease or increase with focal length

List distance of distinct vision

58 / 66

Chromatic aberration can be removed by using

concave lens

combination of concave and convex lenses

two concave lenses

59 / 66

The power of a concave lens is

real

virtual

positive

negative

60 / 66

Unit of power of a lens is

Meter

watt

dioptre

horsepower

61 / 66

A camera of 6-cm focal length is used to photograph a distant scene. The distance from the lens to the image is approximately:

NTS 2016 SMBBMC
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) 6 cm

B) 1 m

C) 80 cm

D) 4 m

62 / 66

The minimum distance between an object and its real image in a convex lens is

2 f

2.5 f

3 f

63 / 66

The polarization of light by tourmaline crystals is due to the ______effect.

NTS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) selective diffraction

B) selective reflection

C) selective interference

D) selective absorption

64 / 66

Red light is used in photographic dark room because of:

NUMS 2020
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:

A) More frequency, less wavelength

B) Less frequency, less wavelength

C) Less frequency. more wavelength

D) More frequency. more wavelength

65 / 66

Light signals passes through multimode graded fibre due to

Continuous refraction

Total internal reflection

Both continuous refraction and total internal reflection

Diffraction

66 / 66

The magnifying power of a compound microscope in terms of the magnification of the objective and
magnifying power of the eyepiece is given by

Your score is

The average score is 46%

Why Optical Instruments Matter in Exams

This chapter strengthens understanding of image formation, ray diagrams, and numerical relationships. Moreover, exam questions often test formula application and conceptual clarity rather than lengthy theory. Practicing topic-wise MCQs and short tests helps students improve accuracy and save time. As a result, focused preparation leads to better performance in entry tests.

Smart Preparation Strategy

Students should revise formulas regularly and practice MCQs after completing each concept. In addition, attempting free practice tests and past questions improves confidence and exam readiness. PLS Academy offers structured resources that support effective preparation for Physics Optical Instruments in entry tests and FSC exams.

JazakAllah.