Light – Reflection and Refraction

AI Learning Assistant

I can help you understand Light – Reflection and Refraction better. Ask me anything!

Summarize the main points of Light – Reflection and Refraction.

What are the most important terms to remember here?

Explain this concept like I'm five.

Give me a quick 3-question practice quiz.

CBSE Learning Objectives – Key Concepts & Skills You Must Know

Learning Objectives

Define the concept of dioptre and its significance in lens power.
Explain the relationship between object distance, image distance, and focal length in spherical mirrors and lenses.
Describe the behavior of light rays when passing through convex and concave lenses.
Identify the characteristics of images formed by different types of mirrors and lenses.
Apply the New Cartesian Sign Convention in solving problems related to mirrors and lenses.
Calculate the magnification produced by mirrors and lenses based on given parameters.

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 9: Light - Reflection and Refraction

9.1 Introduction to Light

Light travels in straight lines.
Mirrors and lenses form images of objects, which can be real or virtual.
The laws of reflection and refraction govern the behavior of light.

9.2 Spherical Mirrors

Types of Spherical Mirrors

Concave Mirror: Curved inwards, converges light rays.
Convex Mirror: Curved outwards, diverges light rays.

Key Terms

Pole (P): The center point of the mirror's reflecting surface.
Focus (F): The point where light rays converge.
Center of Curvature (C): The center of the sphere from which the mirror is a part.

Mirror Formula and Magnification

Mirror Formula:

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$
Where:
- f = focal length
- v = image distance
- u = object distance
Magnification (m):

$m = \frac{h'}{h} = -\frac{v}{u}$
Where:
- h' = height of the image
- h = height of the object

9.3 Spherical Lenses

Types of Lenses

Convex Lens: Converging lens, thicker in the middle.
Concave Lens: Diverging lens, thicker at the edges.

Lens Formula and Power

Lens Formula:

$\frac{1}{f} = \frac{1}{v} + \frac{1}{u}$
Power of a Lens (P):
- SI unit: Dioptre (D)
- $P = \frac{1}{f}$ (f in meters)
- 1 Dioptre = 1 m⁻¹

Sign Convention for Lenses

Focal length of a convex lens is positive.
Focal length of a concave lens is negative.

9.4 Image Formation by Lenses

Ray Diagrams

Convex Lens: Shows various positions of the object and the nature of the image formed.
Concave Lens: Illustrates image formation for different object positions.

9.5 Questions for Review

Define 1 dioptre of power of a lens.
Where is the needle placed in front of a convex lens if the image is equal to the size of the object?
Find the power of a concave lens of focal length 2 m.

9.6 Important Concepts

Light rays bend towards the normal when entering a denser medium and away from the normal when entering a rarer medium.
The refractive index is the ratio of the speed of light in vacuum to that in the medium.

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Misunderstanding the Sign Convention: Students often forget to apply the correct sign convention for distances in mirror and lens formulas. Remember that for mirrors, distances measured in the direction of the incident light are negative, while for lenses, distances measured from the optical center are positive for convex lenses and negative for concave lenses.
Confusing Image Types: It's common to confuse virtual and real images. Virtual images are always erect and formed by concave mirrors when the object is within the focal length, while real images are inverted and can be formed by both concave and convex mirrors depending on the object position.
Incorrect Application of Formulas: Students sometimes mix up the mirror formula and lens formula. Ensure you use the correct formula for the type of optical device you are dealing with:
- Mirror Formula: $rac{1}{f} = rac{1}{v} + rac{1}{u}$
- Lens Formula: $rac{1}{f} = rac{1}{v} + rac{1}{u}$

Tips for Success

Draw Ray Diagrams: Always draw ray diagrams for problems involving mirrors and lenses. This helps visualize the situation and understand the nature of the image formed.
Practice with Different Scenarios: Work through various problems involving different object placements relative to the focal point and center of curvature to solidify your understanding of image formation.
Review Key Definitions: Make sure you understand key terms such as focal length, object distance, image distance, and magnification. Knowing these definitions will help you apply the formulas correctly.
Check Units: When calculating power of lenses, remember that the unit is diopters (D), and it is the reciprocal of the focal length in meters. Always convert focal lengths to meters when calculating power.

CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions

Multiple Choice Questions

18.2°

19.1°

20.5°

21.8°

Correct Answer: A

Solution:

Using Snell's law,

1 \times \sin 30° = 1.6 \times \sin \theta_2

. Solving for

\theta_2

, we get

\sin \theta_2 = \frac{1}{1.6} \times 0.5 = 0.3125

. Therefore,

\theta_2 = \sin^{-1}(0.3125) = 18.2°

Due to reflection of light.

Due to refraction of light.

Due to diffraction of light.

Due to interference of light.

Correct Answer: B

Solution:

The apparent bending of the pencil is due to the refraction of light as it passes from water to air, changing direction at the interface.

2 \times 10^8

m/s

2.5 \times 10^8

m/s

1.5 \times 10^8

m/s

3 \times 10^8

m/s

Correct Answer: A

Solution:

The speed of light in a medium is given by

v = \frac{c}{n}

, where

c

is the speed of light in vacuum and

n

is the refractive index. Thus,

v = \frac{3 \times 10^8}{1.50} = 2 \times 10^8

m/s.

It bends towards the normal.

It bends away from the normal.

It continues in a straight line.

It reflects back into air.

Correct Answer: A

Solution:

When light travels from a less dense medium (air) to a denser medium (water), it bends towards the normal due to a decrease in speed.

Concave lens

Convex lens

Plane lens

Biconcave lens

Correct Answer: B

Solution:

A convex lens converges light rays to a point on the principal axis.

A convex lens of focal length 50 cm

A concave lens of focal length 50 cm

A convex lens of focal length 5 cm

A concave lens of focal length 5 cm

Correct Answer: C

Solution:

A convex lens of short focal length (5 cm) is used for magnification, making it suitable for reading small letters.

Towards the normal

Away from the normal

It does not bend

It reflects back

Correct Answer: A

Solution:

When light travels from a rarer medium to a denser medium, it bends towards the normal.

10 cm behind the mirror

15 cm in front of the mirror

30 cm in front of the mirror

30 cm behind the mirror

Correct Answer: C

Solution:

For a concave mirror, the magnification

m = -\frac{v}{u}

, where

v

is the image distance and

u

is the object distance. Given

m = 3

and

u = -10

cm,

v = -3 \times (-10) = 30

cm, indicating the image is 30 cm in front of the mirror.

5 cm

10 cm

15 cm

20 cm

Correct Answer: B

Solution:

The focal length of a convex lens can be determined by focusing sunlight onto a piece of paper. The distance from the lens to the paper is the focal length, which is 10 cm in this case.

32.1°

28.1°

34.3°

30.0°

Correct Answer: A

Solution:

Using Snell's Law,

n_1 \sin \theta_1 = n_2 \sin \theta_2

, where

n_1 = 1

(air),

\theta_1 = 45°

, and

n_2 = 1.33

. Solving for

\theta_2

gives

\sin \theta_2 = \frac{\sin 45°}{1.33} = 0.5445

, resulting in

\theta_2 \approx 32.1°

The image is real and inverted.

The image is virtual and erect.

The image is larger than the object.

The image is formed on the same side as the object.

Correct Answer: B

Solution:

A plane mirror forms a virtual and erect image that is the same size as the object and appears to be behind the mirror.

The image is real and inverted.

The image is virtual and upright.

The image is real and upright.

The image is virtual and inverted.

Correct Answer: B

Solution:

A plane mirror always forms a virtual image that is upright and the same size as the object.

They diverge.

They converge at a point.

They remain parallel.

They reflect back.

Correct Answer: B

Solution:

Parallel rays of light passing through a convex lens converge at the principal focus of the lens.

10 cm

15 cm

20 cm

30 cm

Correct Answer: A

Solution:

For a real image, the magnification

m = \frac{v}{u} = 2

. Given

u = -15

cm,

v = 30

cm. Using the lens formula

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

, we find

f = 10

cm.

Concave lens

Convex lens

Cylindrical lens

Biconcave lens

Correct Answer: B

Solution:

A convex lens is thicker at the center than at the edges and is also known as a converging lens.

The speed of light increases.

The speed of light decreases.

The speed of light remains the same.

The speed of light first increases then decreases.

Correct Answer: B

Solution:

The speed of light decreases when it enters a medium with a higher refractive index, such as glass.

19.47°

22.02°

25.00°

30.00°

Correct Answer: A

Solution:

Using Snell's Law,

n_1 \sin(i) = n_2 \sin(r)

. Here,

n_1 = 1

(air),

n_2 = 1.5

(glass),

i = 30°

. Solving for

r

, we get

\sin(r) = \frac{\sin(30°)}{1.5} = \frac{0.5}{1.5} = \frac{1}{3}

. Thus,

r = \sin^{-1}(\frac{1}{3}) \approx 19.47°

It continues in a straight line.

It bends towards the normal.

It bends away from the normal.

It reflects back into the air.

Correct Answer: B

Solution:

When light enters a denser medium like glass from a less dense medium like air, it bends towards the normal due to refraction.

Plane mirror

Concave mirror

Convex mirror

Both plane and convex mirrors

Correct Answer: D

Solution:

Both plane and convex mirrors always produce erect images. Plane mirrors produce virtual images that are the same size as the object, while convex mirrors produce smaller, virtual images.

30°

60°

90°

120°

Correct Answer: B

Solution:

According to the law of reflection, the angle of incidence is equal to the angle of reflection. Therefore, the angle between the incident ray and the reflected ray is

30° + 30° = 60°

6 cm behind the mirror

10 cm behind the mirror

5 cm behind the mirror

8 cm behind the mirror

Correct Answer: A

Solution:

Using the mirror formula

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

where

f = 15\, \text{cm}

and

u = -10\, \text{cm}

, solving gives

v = 6\, \text{cm}

. The positive sign indicates the image is virtual and located behind the mirror.

Real and inverted

Virtual and erect

Real and erect

Virtual and inverted

Correct Answer: B

Solution:

When the object is placed between the pole and the focus of a concave mirror, the image formed is virtual, erect, and larger than the object.

24.6°

27.3°

28.1°

30.0°

Correct Answer: B

Solution:

Using Snell's Law:

n_1 \sin \theta_1 = n_2 \sin \theta_2

, where

n_1 = 1.0

(air),

n_2 = 1.6

, and

\theta_1 = 45°

. Solving for

\theta_2

gives

\theta_2 = \sin^{-1}(\frac{1.0 \cdot \sin 45°}{1.6}) = \sin^{-1}(\frac{0.7071}{1.6}) \approx 27.3°

30 cm on the same side as the object

30 cm on the opposite side of the lens

20 cm on the same side as the object

20 cm on the opposite side of the lens

Correct Answer: B

Solution:

Using the lens formula

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

, where

f = 10

cm and

u = -15

cm (object distance is taken as negative for lenses). Solving gives

\frac{1}{v} = \frac{1}{10} + \frac{1}{15} = \frac{5}{30} = \frac{1}{6}

, so

v = 30

cm on the opposite side of the lens.

Concave lens

Convex lens

Biconcave lens

Plane lens

Correct Answer: B

Solution:

A convex lens converges light rays to a focal point, concentrating sunlight onto a small area, which can generate enough heat to start a fire.

10 cm

15 cm

20 cm

30 cm

Correct Answer: A

Solution:

Using the mirror formula

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

and magnification

m = \frac{-v}{u} = 2

, we have

v = -2u = -30

cm. Substituting

u = -15

cm and

v = -30

cm into the mirror formula gives

f = 10

cm.

It increases.

It decreases.

It remains the same.

It first increases then decreases.

Correct Answer: B

Solution:

Light slows down when it enters a denser medium like water from a less dense medium like air.

It increases.

It decreases.

It remains the same.

It becomes zero.

Correct Answer: B

Solution:

Light slows down when it enters a medium with a higher refractive index, such as glass.

Plane mirror

Concave mirror

Convex mirror

Cylindrical mirror

Correct Answer: B

Solution:

Concave mirrors are used in car headlights to focus light into a beam because they converge light rays to a focal point.

Real, inverted, and smaller

Virtual, erect, and smaller

Real, erect, and larger

Virtual, inverted, and larger

Correct Answer: B

Solution:

For a concave lens, the image is always virtual, erect, and smaller than the object, regardless of the object's position.

Real, inverted, and smaller

Real, inverted, and larger

Virtual, upright, and smaller

Virtual, upright, and larger

Correct Answer: B

Solution:

Using the lens formula

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

, where

f = 20

cm and

u = -60

cm, we find

v = 30

cm. The positive value indicates a real image, and the magnification

m = -\frac{v}{u} = 0.5

, indicating the image is inverted and larger.

66.67 cm

150 cm

100 cm

50 cm

Correct Answer: A

Solution:

The focal length

f

in meters is given by

f = \frac{1}{P}

, where

P

is the power in diopters. Thus,

f = \frac{1}{1.5} = 0.6667

meters or 66.67 cm.

5 cm

10 cm

15 cm

20 cm

Correct Answer: B

Solution:

The paper should be placed at the focal point of the lens to achieve maximum concentration of sunlight. Hence, the distance should be equal to the focal length of the lens, which is 10 cm.

It bends towards the normal.

It bends away from the normal.

It continues in a straight line.

It reflects back into the air.

Correct Answer: A

Solution:

When light travels from a less dense medium (air) to a denser medium (water), it bends towards the normal due to a decrease in speed.

Light rays diverge from the principal focus.

Light rays converge at the principal focus.

Light rays reflect off the surface of the lens.

Light rays pass through without deviation.

Correct Answer: B

Solution:

A convex lens is a converging lens, meaning it causes parallel rays of light to converge at the principal focus on the opposite side of the lens.

Plane mirror

Concave mirror

Convex mirror

None of the above

Correct Answer: B

Solution:

Concave mirrors are used in car headlights because they focus light into a beam.

Real, inverted, 30 cm from the mirror

Virtual, upright, 30 cm from the mirror

Real, inverted, 6 cm from the mirror

Virtual, upright, 6 cm from the mirror

Correct Answer: A

Solution:

Using the mirror formula

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

, where

f = -10

cm,

u = -15

cm. Solving for

v

, we get

\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{-10} - \frac{1}{-15} = \frac{-3 + 2}{30} = \frac{-1}{30}

. Thus,

v = -30

cm, indicating a real and inverted image 30 cm from the mirror.

The image is real, inverted, and the same size as the object.

The image is virtual, upright, and larger than the object.

The image is real, upright, and smaller than the object.

The image is virtual, inverted, and the same size as the object.

Correct Answer: A

Solution:

When the object is placed at the center of curvature of a concave mirror, the image formed is real, inverted, and of the same size as the object.

It bends towards the normal.

It bends away from the normal.

It continues in a straight line.

It reflects back into the water.

Correct Answer: B

Solution:

When light travels from a denser medium (water) to a rarer medium (air), it bends away from the normal due to the decrease in optical density.

Light rays diverge after passing through the lens.

Light rays converge at the principal focus.

Light rays reflect back along the same path.

Light rays remain parallel after passing through the lens.

Correct Answer: B

Solution:

A convex lens converges parallel rays of light to a point on the principal axis called the principal focus.

Real, inverted, and smaller than the object.

Virtual, erect, and larger than the object.

Real, erect, and larger than the object.

Virtual, inverted, and smaller than the object.

Correct Answer: B

Solution:

When an object is placed between the focal point and a concave mirror, the image formed is virtual, erect, and larger than the object.

It bends towards the normal.

It bends away from the normal.

It passes through undeviated.

It reflects back along the same path.

Correct Answer: C

Solution:

A ray of light passing through the optical center of a lens continues in the same direction without deviation.

Plane mirror

Concave mirror

Convex mirror

Spherical mirror

Correct Answer: B

Solution:

Concave mirrors are used in car headlights because they converge light rays to a focal point, allowing the light to be focused into a beam.

The lens will not produce any image.

The image will be incomplete.

The brightness of the image will decrease.

The focal length of the lens will change.

Correct Answer: C

Solution:

Covering half of a convex lens reduces the amount of light passing through, thus decreasing the brightness of the image, but the entire image is still formed.

Real and inverted

Virtual and upright

Real and upright

Virtual and inverted

Correct Answer: A

Solution:

Using the mirror formula

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

where

f = -20\, \text{cm}

and

u = -30\, \text{cm}

, solving gives

v = -60\, \text{cm}

. The negative sign indicates a real and inverted image.

Concave mirror

Convex mirror

Plane mirror

It can be either concave or convex depending on the situation.

Correct Answer: A

Solution:

A negative focal length indicates a concave mirror, as the focal point is on the same side as the object.

Parallel rays converge at the principal focus.

Parallel rays diverge away from the principal focus.

Light rays pass through the optical center without deviation.

Light rays are reflected back parallel to the principal axis.

Correct Answer: A

Solution:

A convex lens converges parallel rays of light to a point called the principal focus. This is a fundamental property of converging lenses.

1.5

1.33

1.25

1.75

Correct Answer: A

Solution:

The refractive index

n

is given by

n = \frac{c}{v}

, where

c

is the speed of light in vacuum (3 x 10⁸ m/s) and

v

is the speed of light in the medium. Thus,

n = \frac{3 \times 10^8}{2 \times 10^8} = 1.5

60 cm on the opposite side of the lens

40 cm on the opposite side of the lens

15 cm on the same side as the object

10 cm on the same side as the object

Correct Answer: A

Solution:

Using the lens formula

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

, where

f = 20 \text{ cm}

and

u = -30 \text{ cm}

. Solving gives

\frac{1}{v} = \frac{1}{20} + \frac{1}{30} = \frac{5}{60} = \frac{1}{12}

, thus

v = 60 \text{ cm}

The point where parallel rays diverge.

The point where parallel rays converge.

The center of curvature of the lens.

The optical center of the lens.

Correct Answer: B

Solution:

The principal focus of a convex lens is the point on the principal axis where parallel rays of light converge after passing through the lens.

Towards the normal

Away from the normal

It does not bend

It bends parallel to the surface

Correct Answer: A

Solution:

When light enters a denser medium like water from air, it bends towards the normal due to a decrease in speed.

Concave lens, focal length -0.5 m

Convex lens, focal length 0.5 m

Concave lens, focal length 0.5 m

Convex lens, focal length -0.5 m

Correct Answer: A

Solution:

The power of a lens is given by

P = \frac{1}{f}

, where

f

is the focal length in meters. A negative power indicates a concave lens. Thus,

f = \frac{1}{-2.0} = -0.5

Towards the normal

Away from the normal

It does not bend

It bends parallel to the surface

Correct Answer: A

Solution:

When light travels from a less dense medium (air) to a more dense medium (water), it bends towards the normal.

The speed of light increases.

The speed of light decreases.

The frequency of light increases.

The wavelength of light increases.

Correct Answer: B

Solution:

When light enters a denser medium like glass from a less dense medium like air, its speed decreases due to the higher refractive index of glass.

28.1°

30.0°

32.1°

33.7°

Correct Answer: A

Solution:

Using Snell's Law,

n_1 \sin \theta_1 = n_2 \sin \theta_2

, where

n_1 = 1

(air),

n_2 = 1.5

(glass), and

\theta_1 = 45°

. Solving for

\theta_2

gives

\sin \theta_2 = \frac{1}{1.5} \sin 45° = \frac{\sqrt{2}}{3}

, which results in

\theta_2 \approx 28.1°

Concave lens of focal length 10 cm

Concave lens of focal length 5 cm

Convex lens of focal length 10 cm

Convex lens of focal length 5 cm

Correct Answer: D

Solution:

A convex lens of short focal length is used as a magnifying glass. The shorter the focal length, the greater the magnification.

30 cm behind the mirror

30 cm in front of the mirror

10 cm behind the mirror

10 cm in front of the mirror

Correct Answer: B

Solution:

For a magnification of 3 times, the image distance

v

is 3 times the object distance

u

. Thus,

v = 3 \times 10 = 30

cm in front of the mirror.

19.47°

22.02°

24.62°

26.37°

Correct Answer: B

Solution:

Using Snell's Law at each interface:

n_1 \sin \theta_1 = n_2 \sin \theta_2

. First, calculate the angle of refraction in glass:

1.0 \times \sin 30° = 1.5 \times \sin \theta_2

. Solving gives

\theta_2 = 19.47°

. Next, use this angle to find the angle in water:

1.5 \times \sin 19.47° = 1.33 \times \sin \theta_3

. Solving gives

\theta_3 = 22.02°

10 cm

20 cm

30 cm

40 cm

Correct Answer: B

Solution:

The focal length

f

of a spherical mirror is half of its radius of curvature

R

. Thus,

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

cm.

Real, inverted, and reduced

Virtual, upright, and reduced

Real, upright, and enlarged

Virtual, inverted, and enlarged

Correct Answer: B

Solution:

A convex mirror always forms a virtual, upright, and reduced image regardless of the object's position.

Concave mirror

Convex mirror

Plane mirror

Both plane and convex mirrors

Correct Answer: D

Solution:

Both plane and convex mirrors always form virtual and erect images.

The image is real, inverted, and enlarged.

The image is virtual, erect, and enlarged.

The image is real, erect, and reduced.

The image is virtual, inverted, and reduced.

Correct Answer: B

Solution:

When an object is placed between the focus and the pole of a concave mirror, the image formed is virtual, erect, and enlarged.

A concave lens

A convex lens

A plane lens

A cylindrical lens

Correct Answer: B

Solution:

A convex lens converges light rays to a point, known as the principal focus.

Reflection

Refraction

Diffraction

Photoelectric effect

Correct Answer: C

Solution:

Diffraction is a phenomenon that occurs when light bends around the edges of an obstacle, demonstrating its wave nature.

The image is real and inverted.

The image is virtual and erect.

The image is real and erect.

The image is virtual and inverted.

Correct Answer: B

Solution:

A plane mirror always forms a virtual and erect image that is laterally inverted.

Plane mirror

Concave mirror

Convex mirror

None of the above

Correct Answer: B

Solution:

A concave mirror can produce a magnified image when the object is placed between the focal point and the mirror.

The image is real, inverted, and smaller.

The image is virtual, upright, and larger.

The image is real, upright, and larger.

The image is virtual, inverted, and smaller.

Correct Answer: B

Solution:

When an object is placed between the optical center and the focal point of a convex lens, the image formed is virtual, upright, and larger than the object.

Light bends towards the normal.

Light bends away from the normal.

Light continues in a straight line.

Light is absorbed completely.

Correct Answer: B

Solution:

When light travels from a denser medium to a rarer medium, it bends away from the normal due to the increase in speed of light in the rarer medium.

19.47°

20.00°

25.00°

30.00°

Correct Answer: A

Solution:

Using Snell's Law,

n_1 \sin \theta_1 = n_2 \sin \theta_2

, where

n_1 = 1

(air),

\theta_1 = 30°

, and

n_2 = 1.5

. Solving for

\theta_2

gives

\sin \theta_2 = \frac{\sin 30°}{1.5} = \frac{0.5}{1.5} = \frac{1}{3}

. Thus,

\theta_2 = \sin^{-1}(\frac{1}{3}) \approx 19.47°

True or False

Correct Answer: False

Solution:

A concave mirror reflects light rays parallel to the principal axis through the focus, not the center of curvature.

Correct Answer: True

Solution:

The refractive index is a measure of how much the speed of light is reduced inside a medium, affecting the bending of light.

Correct Answer: False

Solution:

A convex lens converges parallel rays of light to a point on the principal axis, known as the principal focus.

Correct Answer: False

Solution:

A plane mirror forms a virtual and erect image, not a real and inverted one.

Correct Answer: False

Solution:

A concave lens diverges parallel rays of light, making them appear to originate from a point on the principal axis.

Correct Answer: True

Solution:

Diffraction occurs when light encounters an obstacle or a slit that is comparable in size to its wavelength, causing it to bend around the obstacle.

Correct Answer: False

Solution:

A convex lens is thicker at the center than at the edges, which allows it to converge light rays.

Correct Answer: True

Solution:

The refractive index is a measure of how much the speed of light is reduced inside a medium compared to vacuum.

Correct Answer: False

Solution:

A convex lens is thicker in the middle than at the edges, which is why it converges light rays.

Correct Answer: True

Solution:

Modern quantum theory reconciles the wave and particle nature of light, explaining its behavior in various phenomena.

Correct Answer: True

Solution:

A concave lens is thicker at the edges than at the middle and diverges light rays, making them appear to originate from a focal point.

Correct Answer: True

Solution:

A concave lens is also known as a diverging lens because it spreads out light rays that are initially parallel.

Correct Answer: True

Solution:

Light appears to travel along straight-line paths in a transparent medium, as indicated by the casting of sharp shadows and the straight-line treatment of optics using rays.

Correct Answer: True

Solution:

A ray of light passing through the optical center of a lens travels without deviation, maintaining its path.

Correct Answer: True

Solution:

In a concave mirror, parallel rays reflect through the focus, as shown in the ray diagrams involving concave mirrors.

Correct Answer: True

Solution:

In a concave lens, parallel rays of light appear to diverge from a point on the principal axis, which is the principal focus.

Correct Answer: False

Solution:

The image formed by a plane mirror is always virtual and erect.

Correct Answer: True

Solution:

A concave mirror can produce a real image, which is formed when light rays actually converge at a point.

Correct Answer: False

Solution:

A concave mirror can form real or virtual images depending on the position of the object relative to the mirror's focal point.

Correct Answer: True

Solution:

The refractive index of a medium is defined as the ratio of the speed of light in vacuum to the speed of light in the medium, and it is always greater than 1 for any medium other than vacuum.

Correct Answer: True

Solution:

The image formed by a plane mirror is always virtual, erect, and of the same size as the object, appearing as far behind the mirror as the object is in front.

Correct Answer: True

Solution:

The refractive index indicates how much slower light travels in the medium than in a vacuum.

Correct Answer: True

Solution:

A convex lens converges parallel rays of light to a point known as the principal focus, which can be used to focus sunlight to a point.

Correct Answer: False

Solution:

A concave mirror can form both real and virtual images depending on the position of the object relative to the focal point.

Correct Answer: True

Solution:

A concave mirror converges parallel rays of light to a single point on the principal axis known as the focus.

Correct Answer: True

Solution:

A convex lens converges light rays to a point, which can generate enough heat to ignite paper.

Correct Answer: True

Solution:

The refractive index is a measure of how much the speed of light is reduced inside a medium compared to vacuum.

Correct Answer: True

Solution:

The image formed by a plane mirror is always laterally inverted, meaning the left and right sides are reversed.

Correct Answer: True

Solution:

The image formed by a plane mirror is always laterally inverted, meaning it is reversed from left to right.

Correct Answer: True

Solution:

According to the laws of reflection, the angle of incidence is equal to the angle of reflection for all reflecting surfaces.

Correct Answer: True

Solution:

Diffraction is the phenomenon where light bends around the edges of small objects, deviating from a straight-line path.

Correct Answer: True

Solution:

A convex lens converges parallel rays from the Sun to form a real image, which can burn paper due to concentrated sunlight.

Correct Answer: False

Solution:

The refractive index is a measure of how much light slows down in a medium, while optical density refers to the medium's ability to absorb light.

Correct Answer: False

Solution:

Light generally travels in straight lines, but it can bend around small obstacles due to diffraction, and its path can change when it enters different media due to refraction.

Correct Answer: False

Solution:

Light travels in straight lines in a transparent medium, but it can bend when entering a different medium due to refraction.

Correct Answer: False

Solution:

A convex lens can form both real and virtual images depending on the object's position relative to the lens.

Correct Answer: True

Solution:

For a convex lens, parallel rays of light converge at the principal focus after passing through the lens, as shown in ray diagrams.

Correct Answer: True

Solution:

A plane mirror always produces a virtual, erect, and laterally inverted image of the same size as the object.

Correct Answer: True

Solution:

A concave mirror can produce a magnified real image when the object is placed between the focal point and the center of curvature.

Correct Answer: True

Solution:

Light appears to travel along straight-line paths in a transparent medium, as indicated by the sharp shadows cast by opaque objects.

Correct Answer: True

Solution:

Light travels in straight lines through transparent media, allowing us to see objects clearly.

Correct Answer: True

Solution:

Light is able to travel through transparent media as it is transmitted through them, allowing us to see objects on the other side.

Correct Answer: True

Solution:

According to the laws of reflection, the angle of incidence is equal to the angle of reflection for all types of reflecting surfaces.

Correct Answer: True

Solution:

A concave mirror can produce a virtual image when the object is placed between the focal point and the mirror.

Light – Reflection and Refraction

AI Learning Assistant

CBSE Learning Objectives – Key Concepts & Skills You Must Know

Learning Objectives

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 9: Light - Reflection and Refraction

9.1 Introduction to Light

9.2 Spherical Mirrors

Types of Spherical Mirrors

Key Terms

Mirror Formula and Magnification

9.3 Spherical Lenses

Types of Lenses

Lens Formula and Power

Sign Convention for Lenses

9.4 Image Formation by Lenses

Ray Diagrams

9.5 Questions for Review

9.6 Important Concepts

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Tips for Success

Multiple Choice Questions

Q1.A ray of light passes from air into a medium with a refractive index of 1.6. If the angle of incidence is 30°, what is the angle of refraction? (Use Snell's law: n1sin⁡θ1=n2sin⁡θ2n_1 \sin \theta_1 = n_2 \sin \theta_2n1​sinθ1​=n2​sinθ2​ where n1=1n_1 = 1n1​=1 for air.)

Correct Answer: A

Q2.If a pencil is partially immersed in water, why does it appear to be bent at the surface?

Correct Answer: B

Q3.What is the speed of light in glass with a refractive index of 1.50, given that the speed of light in vacuum is 3×1083 \times 10^83×108 m/s?

Correct Answer: A

Q4.What happens to a ray of light when it travels from air into water?

Correct Answer: A

Q5.Which type of lens is used to converge light rays to a point?

Correct Answer: B

Q6.Which lens would you use to read small letters in a dictionary?

Correct Answer: C

Q7.A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal?

Correct Answer: A

Q8.A concave mirror forms a real image that is three times the size of the object. If the object is placed 10 cm from the mirror, where is the image located?

Correct Answer: C

Q9.A convex lens is used to focus sunlight onto a piece of paper. What is the focal length of the lens if the distance from the lens to the paper is 10 cm?

Correct Answer: B

Q10.A light ray travels from air into a medium with a refractive index of 1.33. If the angle of incidence is 45°, what is the angle of refraction in the medium?

Correct Answer: A

Q11.Which of the following is true about the image formed by a plane mirror?

Correct Answer: B

Q12.A plane mirror is used in an experiment. Which of the following is true about the image formed by the plane mirror?

Correct Answer: B

Q13.What happens to parallel rays of light when they pass through a convex lens?

Correct Answer: B

Q14.A lens is used to form a real image on a screen. If the image is twice the size of the object and the object is placed 15 cm from the lens, what is the focal length of the lens?

Correct Answer: A

Q15.Which type of lens is thicker at the center than at the edges?

Correct Answer: B

Q16.When light travels from air into a glass slab, which of the following statements is true about the speed of light?

Correct Answer: B

Q17.A ray of light traveling in air enters obliquely into a glass slab with a refractive index of 1.5. If the angle of incidence is 30°, what is the angle of refraction inside the glass?

Correct Answer: A

Q18.What happens to the path of light when it passes from air into a glass slab?

Correct Answer: B

Q19.Which type of mirror always produces an erect image, regardless of the distance of the object?

Correct Answer: D

Q20.A beam of light is incident on a plane mirror at an angle of 30° to the normal. What is the angle between the incident ray and the reflected ray?

Correct Answer: B

Q21.An object is placed at 10 cm in front of a convex mirror with a focal length of 15 cm. What is the position of the image?

Correct Answer: A

Q22.What is the nature of the image formed by a concave mirror when the object is placed between the pole and the focus?

Correct Answer: B

Q23.A ray of light passes from air into a medium with a refractive index of 1.6. If the angle of incidence in air is 45°, what is the angle of refraction in the medium?

Correct Answer: B

Q24.A convex lens has a focal length of 10 cm. If an object is placed at a distance of 15 cm from the lens, where is the image formed?

Correct Answer: B

Q25.Which type of lens would you use to focus sunlight onto a piece of paper to start a fire?

Correct Answer: B

Q26.A concave mirror forms an image that is twice the size of the object. If the object is placed 15 cm from the mirror, what is the focal length of the mirror?

Correct Answer: A

Q27.When light travels from air into water, how does the speed of light change?

Correct Answer: B

Q28.When light travels from air into a glass slab, what happens to its speed?

Correct Answer: B