Geometrical Optics - 100 Advanced & Numerical with Answers & Explanations

100 Advanced & Numerical MCQs (Level -2) on Geometrical Optics, Physics (Unit-Wise MCQs Practice):
👉Physics MCQs Hub – Unit wise Physics MCQs Practice (Main-Page)👈
Whether you are preparing for board examinations, chapter tests, college assessments, or competitive entrance exams (MDCAT, ECAT, NUST, PIEAS, GIKI, UET, FAST, and other engineering or medical admission tests), this comprehensive MCQ collection is designed to help you master Unit 16 – Geometrical Optics. The questions progress from basic concepts to advanced numerical problems and higher-order thinking skills, ensuring complete and systematic exam preparation.
This chapter-wise MCQ collection includes:
100 Basic MCQs Level -1 (1 - 100) Reflection, refraction, mirrors, lenses, prisms, refractive index, optical instruments, and vision defects.
100 Advanced & Numerical MCQs (101 -200): Mirror and lens formulae, magnification, lens power, Snell's law, prism calculations, critical angle, total internal reflection, and numerical applications.
50 Higher-Order Thinking Skills (HOTS) MCQs 201 - 250): Analytical reasoning, conceptual understanding, Board-inspired questions, practical applications, and competitive exam-level problems.
50 Challenging MCQs Quiz with Answers: A carefully selected mix of conceptual, numerical, and HOTS questions for quick revision, self-assessment, and complete exam preparation.
Key Topics Covered
Reflection and refraction of light
Plane, concave, and convex mirrors
Convex and concave lenses
Mirror and lens formulae
Magnification and lens power
Refractive index and Snell's law
Apparent depth, prisms, and dispersion
Critical angle and total internal reflection
Optical fibres and optical instruments
Human eye and common vision defects
Every MCQ includes the correct answer with a clear concept-based explanation to strengthen understanding, improve problem-solving skills, and build confidence in objective-type questions.
With 250 carefully selected MCQs arranged into 100 Basic, 100 Advanced & Numerical, and 50 HOTS questions, plus a 50-question Challenging MCQs Quiz, this all-in-one question bank provides complete preparation for Unit 16 – Geometrical Optics and helps students excel in both board examinations and competitive entrance tests.
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Geometrical Optics MCQs Level 2 – 100 Advanced & Numerical MCQs (101–200)

MCQ No. 101

An object is placed 30 cm in front of a concave mirror having a focal length of 15 cm. The image will be formed at:

a. 15 cm

b. 20 cm

c. 30 cm

d. Infinity

Correct answer: c

Explanation: Using the mirror formula:

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}

Using the Cartesian sign convention:

$f=-15$ cm
$u=-30$ cm

\frac{1}{-15}=\frac{1}{-30}+\frac{1}{v}

\frac{1}{v}=-\frac{1}{30}

v = - 30 cm

The negative sign indicates that the image is real and formed in front of the mirror.

MCQ No. 102

A concave mirror has a radius of curvature of 40 cm. Its focal length is:

a. 10 cm

b. 20 cm

c. 40 cm

d. 80 cm

Correct answer: b

Explanation: The relationship between focal length and radius of curvature is:

f=\frac{R}{2}

Therefore,

f = \frac{40}{2} = 20 cm

MCQ No. 103

A convex mirror has a focal length of 20 cm. Its radius of curvature is:

a. 10 cm

b. 20 cm

c. 40 cm

d. 80 cm

Correct answer: c

Explanation: For every spherical mirror,

R=2f

Hence,

R = 2 \times 20 = 40 cm

MCQ No. 104

A real image formed by a concave mirror is always:

a. Erect

b. Inverted

c. Virtual

d. Same size

Correct answer: b

Explanation: Real images produced by concave mirrors are always inverted because reflected rays actually meet in front of the mirror.

MCQ No. 105

An object is placed at the principal focus of a concave mirror. The image is formed:

a. At the pole

b. At the center of curvature

c. At infinity

d. Behind the mirror

Correct answer: c

Explanation: When the object is at the focus, the reflected rays become parallel, so the image is formed at infinity.

MCQ No. 106

The magnification produced by a mirror is −2. This means the image is:

a. Virtual and erect

b. Real, inverted, and twice the size of the object

c. Real and diminished

d. Virtual and diminished

Correct answer: b

Explanation: A negative magnification indicates an inverted (real) image, while a magnitude greater than 1 indicates magnification.

MCQ No. 107

The magnification produced by a convex mirror is always:

a. Greater than 1

b. Equal to 1

c. Positive but less than 1

d. Negative

Correct answer: c

Explanation: A convex mirror always forms a virtual, erect, and diminished image, so magnification is positive and less than one.

MCQ No. 108

A concave mirror forms an image equal in size to the object when the object is placed at:

a. Principal focus

b. Pole

c. Center of curvature

d. Infinity

Correct answer: c

Explanation: At the center of curvature, the image is also formed at the center of curvature with the same size as the object.

MCQ No. 109

A shaving mirror is usually:

a. Plane

b. Convex

c. Concave

d. Cylindrical

Correct answer: c

Explanation: A concave mirror forms a magnified, upright image when the face is within its focal length.

MCQ No. 110

Vehicle rear-view mirrors are generally:

a. Plane mirrors

b. Concave mirrors

c. Convex mirrors

d. Parabolic mirrors

Correct answer: c

Explanation: Convex mirrors provide a wide field of view and always form erect, diminished images.

MCQ No. 111

Light travels fastest in:

a. Glass

b. Water

c. Air

d. Vacuum

Correct answer: d

Explanation: The speed of light is maximum in a vacuum ( $3.0\times10^8$ m/s).

MCQ No. 112

If the refractive index of a medium is 1.5, the speed of light in that medium is:

a. $1.5\times10^8$

b. $2.0\times10^8$

c. $2.5\times10^8$

d. $3.0\times10^8$

Correct answer: b

Explanation:

n=\frac{c}{v}

v = \frac{3 \times 10^{8}}{1.5} = 2 \times 10^{8} m/s

MCQ No. 113

If light enters water from air, its:

a. Speed increases

b. Frequency increases

c. Speed decreases

d. Frequency decreases

Correct answer: c

Explanation: Light slows down in water because water has a higher refractive index than air. Its frequency remains unchanged.

MCQ No. 114

According to Snell's law,

n=\frac{\sin i}{\sin r}

when light passes from:

a. Vacuum to vacuum

b. Air into a medium

c. Water into air

d. Glass into water only

Correct answer: b

Explanation: When air is taken as the first medium ( $n\approx1$ ), the refractive index of the second medium is:

n = \frac{\sin i}{\sin r}

MCQ No. 115

A ray of light passes normally through a glass slab. It:

a. Deviates towards the normal

b. Deviates away from the normal

c. Emerges without deviation

d. Undergoes total internal reflection

Correct answer: c

Explanation: At normal incidence ( $i=0^\circ$ ), the ray enters and emerges along the same straight line without bending.

MCQ No. 116

The refractive index of water is approximately:

a. 1.00

b. 1.33

c. 1.50

d. 2.42

Correct answer: b

Explanation: Pure water has an average refractive index of about 1.33.

MCQ No. 117

The refractive index of ordinary glass is approximately:

a. 1.00

b. 1.20

c. 1.50

d. 2.42

Correct answer: c

Explanation: Most optical glass has a refractive index close to 1.5.

MCQ No. 118

Which material has the highest refractive index among the following?

a. Air

b. Water

c. Glass

d. Diamond

Correct answer: d

Explanation: Diamond has a refractive index of approximately 2.42, giving it exceptional brilliance.

MCQ No. 119

A convex lens has a focal length of 25 cm. Its power is:

a. +2 D

b. +4 D

c. +25 D

d. −4 D

Correct answer: b

Explanation:

P=\frac{1}{f}

Convert the focal length into metres:

f=25\text{ cm}=0.25\text{ m}

P = \frac{1}{0.25} = + 4 D

MCQ No. 120

The power of a concave lens having a focal length of −0.50 m is:

a. +2 D

b. −2 D

c. +0.5 D

d. −0.5 D

Correct answer: b

Explanation:

P=\frac{1}{f} =\frac{1}{-0.50} =-2\text{ D}

The negative sign indicates a diverging lens.

MCQ No. 121

A lens of power +5 D has a focal length of:

a. 0.10 m

b. 0.20 m

c. 0.50 m

d. 5.0 m

Correct answer: b

Explanation:

f = \frac{1}{P} = \frac{1}{5} = 0.20 m

MCQ No. 122

A lens with a negative power is always:

a. Convex

b. Plane

c. Concave

d. Cylindrical

Correct answer: c

Explanation: Concave lenses diverge light and therefore have negative focal lengths and negative powers.

MCQ No. 123

The SI unit of focal length is:

a. Centimetre

b. Metre

c. Dioptre

d. Degree

Correct answer: b

Explanation: Focal length is a measure of distance, so its SI unit is the metre.

MCQ No. 124

If a convex lens has a power of +10 D, its focal length is:

a. 0.05 m

b. 0.10 m

c. 0.20 m

d. 10 m

Correct answer: b

Explanation:

f = \frac{1}{10} = 0.10 m = 10 cm

MCQ No. 125

The optical power of a plane glass plate is:

a. +1 D

b. −1 D

c. Infinite

d. 0 D

Correct answer: d

Explanation: A plane glass plate neither converges nor diverges light. Its focal length is effectively infinite, so its power is:

P = \frac{1}{\infty} = 0 D

MCQ No. 126

An object is placed 20 cm in front of a concave mirror of focal length 10 cm. The image is formed:

a. 10 cm in front of the mirror

b. 20 cm in front of the mirror

c. 40 cm in front of the mirror

d. At infinity

Correct answer: b

Explanation: Using the mirror formula,

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}

where $f=-10$ cm and $u=-20$ cm.

\frac{1}{-10}=\frac{1}{-20}+\frac{1}{v}

\frac{1}{v}=-\frac{1}{20}

v=-20\text{ cm}

The image is formed 20 cm in front of the mirror at the center of curvature.

MCQ No. 127

A concave mirror has a focal length of 15 cm. If an object is placed 45 cm in front of it, the image distance is:

a. 18 cm

b. 22.5 cm

c. 30 cm

d. 45 cm

Correct answer: b

Explanation:

Using

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}

\frac{1}{-15}=\frac{1}{-45}+\frac{1}{v}

\frac{1}{v}=-\frac{2}{45}

v=-22.5\text{ cm}

The negative sign indicates a real image in front of the mirror.

MCQ No. 128

A concave mirror produces an image at infinity when the object is placed:

a. At the pole

b. Between the pole and focus

c. At the principal focus

d. Beyond the center of curvature

Correct answer: c

Explanation: When the object is placed at the principal focus, reflected rays become parallel and meet at infinity.

MCQ No. 129

A convex mirror has a focal length of 20 cm. An object is placed 40 cm in front of it. The image formed is:

a. Real

b. Virtual

c. Inverted

d. Same size as the object

Correct answer: b

Explanation: A convex mirror always forms a virtual, erect, and diminished image behind the mirror, regardless of the object's position.

MCQ No. 130

A mirror forms an image three times larger than the object. The magnitude of magnification is:

a. 1/3

b. 1

c. 3

d. 9

Correct answer: c

Explanation: Magnification is the ratio of image size to object size. An image three times larger has a magnification of 3.

MCQ No. 131

The image formed by a concave mirror is virtual when the object is placed:

a. Beyond the center of curvature

b. At the center of curvature

c. Between the pole and the principal focus

d. At infinity

Correct answer: c

Explanation: When the object lies within the focal length of a concave mirror, the image is virtual, erect, and magnified.

MCQ No. 132

A convex lens has a focal length of 20 cm. An object is placed 40 cm from the lens. The image is formed:

a. At the optical center

b. At the principal focus

c. 40 cm on the opposite side

d. At infinity

Correct answer: c

Explanation:

Using the lens formula:

\frac{1}{f}=\frac{1}{v}-\frac{1}{u}

where $f=+20$ cm and $u=-40$ cm,

\frac{1}{20}=\frac{1}{v}+\frac{1}{40}

\frac{1}{v}=\frac{1}{40}

v = 40 cm

The image is formed at twice the focal length on the opposite side of the lens.

MCQ No. 133

A convex lens forms an image at infinity when the object is placed:

a. At the optical center

b. At twice the focal length

c. At the principal focus

d. Beyond twice the focal length

Correct answer: c

Explanation: When the object is at the principal focus of a convex lens, the refracted rays emerge parallel, producing an image at infinity.

MCQ No. 134

A concave lens always forms an image that is:

a. Real and inverted

b. Real and magnified

c. Virtual, erect, and diminished

d. Virtual and magnified

Correct answer: c

Explanation: A concave lens always forms a virtual, erect, and smaller image on the same side as the object.

MCQ No. 135

An object is placed at a very large distance from a convex lens. The image is formed:

a. At infinity

b. At the optical center

c. At the principal focus

d. At twice the focal length

Correct answer: c

Explanation: Light rays from a distant object are nearly parallel and converge at the principal focus after passing through a convex lens.

MCQ No. 136

The refractive index of a medium is 1.5. The critical angle is approximately:

a. 30°

b. 42°

c. 60°

d. 75°

Correct answer: b

Explanation: For light traveling from the denser medium to air,

\sin C=\frac{1}{n}

\sin C=\frac{1}{1.5}=0.667

C \approx {41.8}^{\circ} \approx 42^{\circ}

MCQ No. 137

Total internal reflection occurs only when the angle of incidence is:

a. Equal to the critical angle

b. Less than the critical angle

c. Greater than the critical angle

d. Equal to zero

Correct answer: c

Explanation: At angles greater than the critical angle, the light is completely reflected back into the denser medium.

MCQ No. 138

An optical fibre transmits light through repeated:

a. Refraction

b. Diffraction

c. Total internal reflection

d. Interference

Correct answer: c

Explanation: Light continuously undergoes total internal reflection within the fibre core, enabling efficient transmission.

MCQ No. 139

The apparent depth of a pond is 2 m. If the refractive index of water is 1.33, the real depth is approximately:

a. 1.5 m

b. 2.0 m

c. 2.66 m

d. 3.33 m

Correct answer: c

Explanation:

n=\frac{\text{Real depth}}{\text{Apparent depth}}

Real depth = 1.33 \times 2 = 2.66 m

MCQ No. 140

A coin placed under water appears raised because:

a. Reflection occurs

b. Light bends away from the normal while emerging into air

c. Light bends toward the normal

d. Total internal reflection occurs

Correct answer: b

Explanation: As light passes from water to air, it bends away from the normal, making the coin appear closer to the surface.

MCQ No. 141

A lens has a focal length of 0.5 m. Its power is:

a. +0.5 D

b. +1 D

c. +2 D

d. +5 D

Correct answer: c

Explanation:

P = \frac{1}{f} = \frac{1}{0.5} = 2 D

MCQ No. 142

The focal length of a lens having a power of −4 D is:

a. −0.25 m

b. +0.25 m

c. −4 m

d. +4 m

Correct answer: a

Explanation:

f = \frac{1}{P} = \frac{1}{- 4} = - 0.25 m

The negative sign indicates a concave lens.

MCQ No. 143

Two thin lenses of powers +2 D and +3 D are placed in contact. Their combined power is:

a. +1 D

b. +5 D

c. +6 D

d. +9 D

Correct answer: b

Explanation: The equivalent power of thin lenses in contact is the sum of their individual powers:

P = P_{1} + P_{2} = 2 + 3 = 5 D

MCQ No. 144

Two lenses of powers +5 D and −2 D are placed together. Their equivalent power is:

a. +7 D

b. +3 D

c. −3 D

d. −7 D

Correct answer: b

Explanation:

P = 5 + (- 2) = 3 D

MCQ No. 145

A person cannot see distant objects clearly. The defect is corrected using:

a. Convex lens

b. Concave lens

c. Plane mirror

d. Prism

Correct answer: b

Explanation: Myopia (short-sightedness) is corrected using a concave (diverging) lens, which helps focus distant objects on the retina.

MCQ No. 146

Hypermetropia is corrected by using a:

a. Concave lens

b. Convex lens

c. Cylindrical lens

d. Plane glass plate

Correct answer: b

Explanation: Hypermetropia (long-sightedness) is corrected using a convex (converging) lens.

MCQ No. 147

The near point of a normal human eye is approximately:

a. 10 cm

b. 15 cm

c. 25 cm

d. 50 cm

Correct answer: c

Explanation: A normal eye can see objects clearly as close as 25 cm, known as the least distance of distinct vision.

MCQ No. 148

The far point of a normal human eye is:

a. 25 cm

b. 50 cm

c. 100 cm

d. Infinity

Correct answer: d

Explanation: A healthy human eye can focus on distant objects effectively up to infinity.

MCQ No. 149

Which optical instrument is primarily used to observe very distant celestial objects?

a. Compound microscope

b. Simple microscope

c. Astronomical telescope

d. Periscope

Correct answer: c

Explanation: An astronomical telescope uses lenses or mirrors to collect and magnify light from distant celestial bodies.

MCQ No. 150

A simple microscope is essentially a:

a. Concave mirror

b. Convex lens of short focal length

c. Concave lens

d. Plane mirror

Correct answer: b

Explanation: A simple microscope is a single convex lens with a short focal length that produces a magnified virtual image of a nearby object.

MCQ No. 151

A concave mirror has a focal length of 12 cm. An object is placed 24 cm in front of it. The image formed will be:

a. 12 cm in front of the mirror

b. 24 cm in front of the mirror

c. 36 cm in front of the mirror

d. At infinity

Correct answer: b

Explanation: Since the object is placed at 2f (24 cm), the image is also formed at 2f. Using the mirror formula confirms that v = -24 cm.

MCQ No. 152

An object is placed 10 cm in front of a convex mirror having a focal length of 15 cm. The image formed is:

a. Real and inverted

b. Virtual and behind the mirror

c. Real and magnified

d. At infinity

Correct answer: b

Explanation: A convex mirror always produces a virtual, erect, and diminished image behind the mirror, irrespective of the object's position.

MCQ No. 153

A concave mirror forms an image 60 cm in front of the mirror when an object is 20 cm away. The focal length of the mirror is:

a. 10 cm

b. 15 cm

c. 20 cm

d. 30 cm

Correct answer: b

Explanation:

Using the mirror formula:
$\frac{1}{f}=\frac{1}{u}+\frac{1}{v}$
With the Cartesian sign convention:

$u=-20$

$v=-60$

$\frac{1}{f}=-\frac{1}{20}-\frac{1}{60} =-\frac{4}{60} =-\frac{1}{15}$
Therefore,
$f = - 15 cm$
The focal length is 15 cm.

MCQ No. 154

A convex lens has a focal length of 30 cm. An object is placed 60 cm from the lens. The image will be formed:

a. 15 cm from the lens

b. 30 cm from the lens

c. 60 cm from the lens

d. At infinity

Correct answer: c

Explanation: An object placed at 2f forms a real, inverted image of the same size at 2f on the opposite side of the lens.

MCQ No. 155

A convex lens forms an image at 30 cm when an object is placed 15 cm away. The focal length of the lens is:

a. 10 cm

b. 15 cm

c. 20 cm

d. 30 cm

Correct answer: a

Explanation:

Using the lens formula:
$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$
where

$u=-15$

$v=+30$

$\frac{1}{f}=\frac{1}{30}+\frac{1}{15} =\frac{3}{30} =\frac{1}{10}$
Hence,
$f = 10 cm$

MCQ No. 156

The power of a convex lens having a focal length of 50 cm is:

a. +1 D

b. +2 D

c. +4 D

d. +5 D

Correct answer: b

Explanation:
$P = \frac{1}{f} = \frac{1}{0.50} = + 2 D$

MCQ No. 157

A concave lens has a focal length of −25 cm. Its power is:

a. −2 D

b. −4 D

c. +2 D

d. +4 D

Correct answer: b

Explanation:
$P = \frac{1}{- 0.25} = - 4 D$

MCQ No. 158

Two convex lenses of powers +4 D and +6 D are placed in contact. Their equivalent focal length is:

a. 5 cm

b. 10 cm

c. 20 cm

d. 25 cm

Correct answer: b

Explanation:

Equivalent power:
$P=4+6=10\text{ D}$
Therefore,
$f = \frac{1}{10} = 0.10 m = 10 cm$

MCQ No. 159

The speed of light in a medium is $1.5\times10^8$ m/s. The refractive index of the medium is:

a. 1.2

b. 1.5

c. 2.0

d. 3.0

Correct answer: c

Explanation:
$n = \frac{c}{v} = \frac{3 \times 10^{8}}{1.5 \times 10^{8}} = 2$

MCQ No. 160

Light enters glass from air at an angle of incidence of 0°. The angle of refraction is:

a. 30°

b. 45°

c. 90°

d. 0°

Correct answer: d

Explanation: When light strikes the surface normally, it continues straight without bending.

MCQ No. 161

A ray passes from water into air with an angle of incidence greater than the critical angle. It will undergo:

a. Diffraction

b. Dispersion

c. Total internal reflection

d. Polarization

Correct answer: c

Explanation: Light is completely reflected back into water when the angle of incidence exceeds the critical angle.

MCQ No. 162

The critical angle for diamond is much smaller than that of glass because diamond has:

a. Lower density

b. Lower refractive index

c. Higher refractive index

d. Higher transparency

Correct answer: c

Explanation: Diamond's high refractive index (about 2.42) produces a small critical angle, allowing multiple total internal reflections.

MCQ No. 163

The refractive index of water is 1.33. If the real depth of a pond is 4 m, its apparent depth is approximately:

a. 2.0 m

b. 2.5 m

c. 3.0 m

d. 5.3 m

Correct answer: c

Explanation:
$Apparent depth = \frac{Real depth}{n} = \frac{4}{1.33} \approx 3.0 m$

MCQ No. 164

A person standing outside a swimming pool sees the bottom shallower due to:

a. Reflection

b. Refraction

c. Diffraction

d. Interference

Correct answer: b

Explanation: Refraction at the water-air surface makes underwater objects appear raised.

MCQ No. 165

A prism deviates light because:

a. Its two refracting surfaces are not parallel.

b. It absorbs light.

c. It reflects all incident rays.

d. It changes the frequency of light.

Correct answer: a

Explanation: Since the refracting faces of a prism are inclined to each other, the emergent ray deviates from its original direction.

MCQ No. 166

Which colour experiences the greatest deviation while passing through a prism?

a. Red

b. Yellow

c. Green

d. Violet

Correct answer: d

Explanation: Violet light has the shortest wavelength and the highest refractive index in glass, resulting in the greatest deviation.

MCQ No. 167

The colour deviated the least by a prism is:

a. Violet

b. Blue

c. Green

d. Red

Correct answer: d

Explanation: Red light has the longest wavelength and therefore experiences the least refraction.

MCQ No. 168

The splitting of sunlight into seven colours by a prism is known as:

a. Reflection

b. Polarization

c. Dispersion

d. Scattering

Correct answer: c

Explanation: Dispersion occurs because different colours have different wavelengths and refractive indices.

MCQ No. 169

A simple microscope uses:

a. One convex lens

b. One concave lens

c. Two convex lenses

d. One convex mirror

Correct answer: a

Explanation: A simple microscope is a magnifying glass consisting of a single convex lens.

MCQ No. 170

In a compound microscope, the objective lens has:

a. Long focal length

b. Short focal length

c. Infinite focal length

d. Zero focal length

Correct answer: b

Explanation: The objective lens has a very short focal length to produce a highly magnified real image.

MCQ No. 171

The eyepiece of a compound microscope acts as a:

a. Plane mirror

b. Magnifying glass

c. Prism

d. Concave lens

Correct answer: b

Explanation: The eyepiece further magnifies the real image formed by the objective lens.

MCQ No. 172

An astronomical telescope is mainly used to observe:

a. Microorganisms

b. Nearby objects

c. Distant celestial bodies

d. Small printed letters

Correct answer: c

Explanation: Astronomical telescopes are designed to collect light from distant stars, planets, and galaxies.

MCQ No. 173

The objective lens of an astronomical telescope has:

a. Short focal length

b. Long focal length

c. Negative focal length

d. Zero focal length

Correct answer: b

Explanation: A long focal length objective gathers more light and forms a clear image of distant objects.

MCQ No. 174

The reflecting telescope uses a:

a. Convex mirror

b. Plane mirror

c. Concave mirror

d. Concave lens

Correct answer: c

Explanation: A large concave mirror collects and focuses light in a reflecting telescope.

MCQ No. 175

Which optical instrument works primarily on the principle of total internal reflection?

a. Simple microscope

b. Optical fibre

c. Convex lens

d. Concave mirror

Correct answer: b

Explanation: Optical fibres guide light through repeated total internal reflections, making them ideal for telecommunications and medical imaging.

MCQ No. 176

An object is placed 15 cm in front of a concave mirror of focal length 10 cm. The image distance is:

a. 20 cm

b. 30 cm

c. 15 cm

d. 10 cm

Correct answer: b

Explanation: Using the mirror formula,

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}

where $f=-10$ cm and $u=-15$ ,

\frac{1}{-10}=\frac{1}{-15}+\frac{1}{v}

\frac{1}{v}=-\frac{1}{30}

v=-30\text{ cm}

The image is formed 30 cm in front of the mirror.

MCQ No. 177

A concave mirror produces an image twice the size of the object. The magnitude of magnification is:

a. 0.5

b. 1

c. 2

d. 4

Correct answer: c

Explanation: Magnification is the ratio of image height to object height. An image twice as large has a magnification of 2.

MCQ No. 178

A convex lens has a focal length of 15 cm. If the object is placed at 30 cm, the image distance is:

a. 15 cm

b. 20 cm

c. 30 cm

d. 45 cm

Correct answer: c

Explanation: Since the object is placed at 2f, the image is also formed at 2f on the opposite side of the lens.

MCQ No. 179

An object is placed 10 cm from a convex lens of focal length 20 cm. The image formed is:

a. Real and inverted

b. Virtual, erect, and magnified

c. Real and diminished

d. Virtual and diminished

Correct answer: b

Explanation: When the object is placed within the focal length of a convex lens, it forms a virtual, erect, and magnified image on the same side of the lens.

MCQ No. 180

A concave lens always produces an image that is:

a. Real and magnified

b. Real and inverted

c. Virtual, erect, and diminished

d. Real and diminished

Correct answer: c

Explanation: Regardless of the object's position, a concave lens always forms a virtual, erect, and diminished image.

MCQ No. 181

The power of a lens is −5 D. Its focal length is:

a. −0.20 m

b. +0.20 m

c. −5.0 m

d. +5.0 m

Correct answer: a

Explanation:

f=\frac{1}{P} =\frac{1}{-5} =-0.20\text{ m}

The negative focal length indicates a concave lens.

MCQ No. 182

Two thin lenses of powers +4 D and −1 D are placed in contact. Their equivalent power is:

a. +3 D

b. +5 D

c. −3 D

d. −5 D

Correct answer: a

Explanation: The equivalent power is the algebraic sum of the individual powers:

P = + 4 + (- 1) = + 3 D

MCQ No. 183

The equivalent focal length of the lens combination in MCQ No. 182 is:

a. 0.20 m

b. 0.25 m

c. 0.33 m

d. 0.50 m

Correct answer: c

Explanation:

f = \frac{1}{P} = \frac{1}{3} \approx 0.33 m

MCQ No. 184

A ray of light enters a rectangular glass slab obliquely. The emergent ray is:

a. Perpendicular to the incident ray

b. Parallel to the incident ray

c. Reflected back

d. At right angles to the surface

Correct answer: b

Explanation: The opposite faces of a rectangular glass slab are parallel, so the emergent ray remains parallel to the incident ray, although it is laterally displaced.

MCQ No. 185

The sideways shift of a ray passing through a glass slab is called:

a. Angular deviation

b. Lateral displacement

c. Dispersion

d. Total reflection

Correct answer: b

Explanation: A ray passing through a parallel-sided glass slab emerges parallel to its original path but is shifted sideways. This is called lateral displacement.

MCQ No. 186

The lateral displacement produced by a glass slab increases with:

a. Decreasing slab thickness

b. Increasing slab thickness

c. Decreasing refractive index

d. Decreasing angle of incidence

Correct answer: b

Explanation: A thicker glass slab causes a greater lateral displacement of the light ray.

MCQ No. 187

Which quantity remains unchanged when light passes from one medium to another?

a. Speed

b. Wavelength

c. Frequency

d. Direction

Correct answer: c

Explanation: The frequency of light is determined by the source and remains constant during refraction, while speed and wavelength change.

MCQ No. 188

The critical angle depends mainly on:

a. Intensity of light

b. Colour of the object

c. Refractive indices of the two media

d. Thickness of the medium

Correct answer: c

Explanation: The critical angle is determined by the refractive indices of the denser and rarer media.

MCQ No. 189

If the refractive index of a medium increases, the critical angle:

a. Increases

b. Remains constant

c. Decreases

d. Becomes 90°

Correct answer: c

Explanation: Since

\sin C=\frac{1}{n},

a larger refractive index results in a smaller critical angle.

MCQ No. 190

The principal function of a prism in binoculars is to:

a. Produce dispersion

b. Increase magnification only

c. Turn the image upright using total internal reflection

d. Absorb unwanted light

Correct answer: c

Explanation: Binoculars use prisms to invert the image correctly and reflect light efficiently by total internal reflection.

MCQ No. 191

A prism used for dispersion separates white light because different colours have different:

a. Intensities

b. Frequencies only

c. Refractive indices in glass

d. Electric charges

Correct answer: c

Explanation: The refractive index of glass varies with wavelength, so each colour bends by a different amount.

MCQ No. 192

A student observes a fish in a pond. The fish appears closer to the surface due to:

a. Reflection

b. Refraction

c. Diffraction

d. Polarization

Correct answer: b

Explanation: Light from the fish bends away from the normal as it passes from water to air, making the fish appear shallower.

MCQ No. 193

The magnifying power of a simple microscope increases when its focal length:

a. Increases

b. Decreases

c. Remains constant

d. Becomes infinite

Correct answer: b

Explanation: A shorter focal length provides greater angular magnification, producing a larger apparent image.

MCQ No. 194

The objective lens of a compound microscope is designed to produce a:

a. Virtual, erect image

b. Real, magnified image

c. Virtual, diminished image

d. Same-size image

Correct answer: b

Explanation: The objective forms a real, enlarged image, which is further magnified by the eyepiece.

MCQ No. 195

In an astronomical telescope under normal adjustment, the final image is formed:

a. At the principal focus of the objective

b. At infinity

c. At the eyepiece

d. At the optical center

Correct answer: b

Explanation: Under normal adjustment, the telescope is arranged so that the final image is at infinity, allowing comfortable viewing.

MCQ No. 196

A reflecting telescope uses a concave mirror because it:

a. Eliminates chromatic aberration

b. Produces greater dispersion

c. Reduces total internal reflection

d. Increases refraction

Correct answer: a

Explanation: Mirrors reflect all wavelengths equally, so reflecting telescopes do not suffer from chromatic aberration like refracting telescopes.

MCQ No. 197

The image formed by a convex mirror is always located:

a. Beyond the center of curvature

b. Between the pole and the principal focus behind the mirror

c. At the center of curvature

d. At infinity

Correct answer: b

Explanation: A convex mirror always forms a virtual image between the pole and the principal focus behind the mirror.

MCQ No. 198

A prism deviates light toward its:

a. Base

b. Apex

c. Center

d. Normal

Correct answer: a

Explanation: The emergent ray from a prism is always deviated toward the base of the prism.

MCQ No. 199

If the angle of incidence equals the critical angle, the refracted ray travels:

a. Toward the normal

b. Away from the normal

c. Along the boundary surface

d. Back into the denser medium

Correct answer: c

Explanation: At the critical angle, the angle of refraction becomes 90°, so the refracted ray travels along the interface.

MCQ No. 200

A student wants to identify an unknown transparent material by measuring the speed of light in it. Which property can then be calculated directly?

a. Density

b. Specific heat capacity

c. Refractive index

d. Thermal conductivity

Correct answer: c

Explanation: Once the speed of light in the material is known, its refractive index can be calculated using:

n=\frac{c}{v}

where $c$ is the speed of light in vacuum and $v$ is the speed of light in the material.

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