Physics Chapter 10 – Optical Instruments (Class 11) for FSC, Entry Tests & NTS Preparation
Chapter 10, Optical Instruments, is an important topic for Class 11 students preparing for FSC board exams, engineering entry tests like ECAT, NUST, FAST, and NTS exams. This chapter explains the working principles, construction, and applications of devices that use lenses and mirrors to produce or enhance images. Understanding optical instruments is essential for studying practical optics and their applications in science and technology.
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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:
Unit of power of a lens is
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:
In going form a denser to rarer medium a array of light is
A convex and concave lens of focal length ‘f’ are in contact, the focal length of the combination will be.
Monochromatic light means the light having:
NUMS 2018
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
The polarization of light by tourmaline crystals is due to the ______effect.
NTS 2019
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
Coherent source of light means?
PMC Practice 3
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
Light signals passes through multimode graded fibre due to
A lens which converges a beam of parallel rays to a point is called
In multimode step index fibre the refractive index of core and cladding is
If an object is placed away form ‘2f’ of a converging lens, then the image will be
If placed in contact, the focal length of the combination of two convex lenses of equal focal lengths f,
will be
The diameter of a lens is called
Wave nature of light is proved by:
PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
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:
- 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?
least distance of distinct vision
The magnifying power of a compound microscope in terms of the magnification of the objective and
magnifying power of the eyepiece is given by
If a single convex lens is placed close to the eye, it can be used as a
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:
The electrical signals change into light signals for transmission through optical fibre. A light pulse
represent.
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
In a scanning electron microscope, image formed is:
PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
A spectrometer is used to find.
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:
The interference of green photon to red photon will cause:
PMC Practice 1
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
Magnifying power of simple microscope
The least distance of distinct vision for a normal eye is
Image of an object 5 mm high is only 1 cm high. Magnification produced by lens is
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:
Dispersional effect may produced error in light signals. This type of error is minimum in.
The least distance of distinct vision for normal eye is approximately
Chromatic aberration can be removed by using
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.
Red light is used in photographic dark room because of:
NUMS 2020
Physics
Optics, Nature of Light and Optical Instruments
Elimination Tool:
A double convex lens acts as a diverging lens when the object is placed
The objective of a microscope is a lens of
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:
White light does not focus to a single point after passing through a convex lens due to
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:
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:
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
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:
There is no noticeable boundary between core and cladding.
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:
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:
Spherical aberration can be reduced by using
Final image produced by a compound microscope is
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 lens, which is thicker at the center and thicker at the edges, is called.
for normal adjustment, length of astronomical telescope is
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 convex lens gives a virtual image only when the objects leis
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:
The power of a concave lens is
Two convex lenses of equal focal length ‘f’ are placed in contact, the resultant focal length of the
combination is
A point where the incident parallel rays of light converge or appear to diverge after passing through a lens
is called
If d is the distance of distinct vision, the magnifying power of a magnifying glass of focal length f is
Dioptre power of an concave lens of 10 cm focal length is
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:
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 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:
The minimum distance between an object and its real image in a convex lens is
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:
Critical angle is that incident angle in denser medium for which angle of refraction is.
Key Concepts about Optical Instruments
The chapter explains the functioning of optical instruments such as the human eye, microscopes, telescopes, and cameras. It covers image formation, magnification, resolution, and adjustments needed for clear imaging. The chapter also discusses the correction of optical defects in lenses and mirrors, and the application of these principles in modern optical devices. Each concept is explained with diagrams, examples, and step-by-step problem-solving methods. These concepts are highly important for FSC board exams, engineering entry tests like ECAT, NUST, FAST, and NTS exams.
Free Entry Test & NTS Preparation
Mastery of optical instruments helps students understand image formation, lens systems, and practical applications in optical technology. PLS Academy provides practice questions, solved past papers, and chapter-wise MCQs to help students revise these topics effectively. Regular study of this chapter improves problem-solving skills, conceptual clarity, and exam performance, ensuring students are well-prepared for FSC board exams, competitive entry tests, and NTS exams.
JazakAllah.
