Class 10 Science Light: Reflection and Refraction Question Bank
A. MCQs — Multiple Choice Questions
1.
The angle of incidence is equal to:
A. angle of refraction
B. angle of reflection
C. angle between mirror and incident ray
D. angle between reflected ray and mirror
Answer: B
2.
The image formed by a plane mirror is:
A. real and inverted
B. virtual and inverted
C. virtual and erect
D. real and erect
Answer: C
3.
The image formed by a plane mirror is:
A. larger than the object
B. smaller than the object
C. equal in size to the object
D. sometimes larger and sometimes smaller
Answer: C
4.
A spherical mirror whose reflecting surface curves inward is called:
A. convex mirror
B. concave mirror
C. plane mirror
D. cylindrical mirror
Answer: B
5.
A spherical mirror whose reflecting surface curves outward is:
A. concave
B. plane
C. convex
D. parabolic
Answer: C
6.
The centre of the reflecting surface of a spherical mirror is called:
A. focus
B. centre of curvature
C. pole
D. optical centre
Answer: C
7.
The relation between focal length and radius of curvature of a spherical mirror is:
A. (f=R)
B. (f=2R)
C. (f=R/2)
D. (R=f/2)
Answer: C
8.
A concave mirror can produce:
A. only real images
B. only virtual images
C. both real and virtual images
D. only erect images
Answer: C
9.
When an object is placed between the pole and focus of a concave mirror, the image is:
A. real, inverted and diminished
B. real, inverted and enlarged
C. virtual, erect and enlarged
D. virtual, inverted and diminished
Answer: C
10.
A convex mirror always produces an image that is:
A. real, inverted and enlarged
B. virtual, erect and diminished
C. real, erect and diminished
D. virtual, inverted and enlarged
Answer: B
11.
Convex mirrors are preferred as rear-view mirrors because they:
A. produce enlarged images
B. produce inverted images
C. provide a wider field of view
D. produce real images
Answer: C
12.
The mirror formula is:
A. (\frac1v-\frac1u=\frac1f)
B. (\frac1v+\frac1u=\frac1f)
C. (v+u=f)
D. (uv=f)
Answer: B
13.
Magnification produced by a spherical mirror is:
A. (m=v/u)
B. (m=u/v)
C. (m=-v/u)
D. (m=f/u)
Answer: C
14.
A negative value of magnification for a spherical mirror indicates that the image is:
A. virtual
B. erect
C. real and inverted
D. diminished only
Answer: C
15.
According to the Cartesian sign convention, distances measured to the left of the pole are:
A. positive
B. negative
C. zero
D. always infinite
Answer: B
16.
The phenomenon responsible for the bending of light at the boundary of two transparent media is:
A. reflection
B. dispersion
C. refraction
D. scattering
Answer: C
17.
When light travels from a rarer medium to a denser medium, it generally bends:
A. away from the normal
B. towards the normal
C. along the surface
D. backwards
Answer: B
18.
When light travels from a denser medium to a rarer medium, it bends:
A. towards the normal
B. away from the normal
C. towards the surface
D. along the normal only
Answer: B
19.
Snell’s law is represented by:
A. (\sin i\sin r=\text{constant})
B. (\frac{\sin i}{\sin r}=\text{constant})
C. (i/r=\text{constant})
D. (i+r=\text{constant})
Answer: B
20.
The speed of light is maximum in:
A. glass
B. water
C. vacuum
D. diamond
Answer: C
21.
The absolute refractive index of a medium is:
A. (v/c)
B. (c/v)
C. (cv)
D. (c+v)
Answer: B
22.
In a rectangular glass slab, the emergent ray is:
A. perpendicular to the incident ray
B. parallel to the incident ray
C. always along the normal
D. always reflected back
Answer: B
23.
A convex lens is also called a:
A. diverging lens
B. converging lens
C. reflecting lens
D. plane lens
Answer: B
24.
A concave lens is:
A. thicker at the centre
B. thicker at the edges
C. equally thick everywhere
D. always plane
Answer: B
25.
A convex lens generally:
A. diverges parallel rays
B. converges parallel rays
C. reflects parallel rays
D. absorbs parallel rays
Answer: B
26.
A concave lens always forms an image that is:
A. real, inverted and enlarged
B. virtual, erect and diminished
C. real, erect and diminished
D. virtual, inverted and enlarged
Answer: B
27.
When an object is placed between F and 2F of a convex lens, the image is:
A. between F and O
B. at F
C. beyond 2F
D. at the optical centre
Answer: C
28.
When an object is placed at 2F of a convex lens, the image is:
A. at F and diminished
B. at 2F and same size
C. beyond 2F and enlarged
D. between F and O
Answer: B
29.
An object placed between F and O of a convex lens produces:
A. real, inverted and diminished image
B. real, inverted and enlarged image
C. virtual, erect and enlarged image
D. virtual, inverted and diminished image
Answer: C
30.
A ray passing through the optical centre of a thin lens:
A. is reflected back
B. bends towards the focus
C. emerges without deviation
D. becomes parallel to the axis
Answer: C
31.
The lens formula is:
A. (\frac1v+\frac1u=\frac1f)
B. (\frac1v-\frac1u=\frac1f)
C. (v-u=f)
D. (uv=f)
Answer: B
32.
Magnification produced by a lens is:
A. (-v/u)
B. (u/v)
C. (v/u)
D. (f/u)
Answer: C
33.
The power of a lens is:
A. (f)
B. (f^2)
C. (1/f)
D. (1/f^2)
Answer: C
34.
The SI unit of lens power is:
A. metre
B. centimetre
C. dioptre
D. watt
Answer: C
35.
The power of a convex lens is:
A. always negative
B. always positive
C. always zero
D. sometimes negative
Answer: B
36.
The power of a concave lens is:
A. positive
B. negative
C. zero
D. infinite
Answer: B
37.
A lens has power (+2D). It is:
A. concave
B. convex
C. plane
D. cylindrical
Answer: B
38.
A lens has power (-2D). It is:
A. convex
B. concave
C. plane
D. spherical mirror
Answer: B
39.
A lens of focal length (1,m) has power:
A. (0.1D)
B. (1D)
C. (10D)
D. (100D)
Answer: B
40.
Two lenses of powers (+2D) and (+0.25D) are in contact. Their combined power is:
A. (+1.75D)
B. (+2.25D)
C. (-2.25D)
D. (+8D)
Answer: B
B. Assertion–Reason Questions
Choose:
A. Both A and R are true, and R correctly explains A.
B. Both A and R are true, but R does not correctly explain A.
C. A is true, but R is false.
D. A is false, but R is true.
1.
Assertion: A convex mirror is used as a rear-view mirror.
Reason: It provides a wider field of view.
Answer: A
2.
Assertion: A concave mirror can produce a virtual image.
Reason: When the object lies between P and F, the reflected rays diverge and their backward extensions meet behind the mirror.
Answer: A
3.
Assertion: A convex mirror always produces an erect image.
Reason: Its image is always virtual and diminished.
Answer: B
4.
Assertion: Light bends towards the normal when travelling from air to glass obliquely.
Reason: Glass is optically denser than air.
Answer: A
5.
Assertion: The emergent ray from a rectangular glass slab is parallel to the incident ray.
Reason: The opposite surfaces of a rectangular glass slab are parallel.
Answer: A
6.
Assertion: A concave lens always produces a virtual image.
Reason: It causes parallel rays to diverge.
Answer: A
7.
Assertion: The power of a convex lens is positive.
Reason: The focal length of a convex lens is positive under the sign convention.
Answer: A
8.
Assertion: A convex lens can form a virtual image.
Reason: An object placed between the optical centre and focus produces an enlarged virtual image.
Answer: A
9.
Assertion: A plane mirror produces a real image.
Reason: Reflected rays actually meet behind the mirror.
Answer: D
10.
Assertion: A lens with shorter focal length has greater power.
Reason: Power is inversely proportional to focal length.
Answer: A
C. Fill in the Blanks
1.
The bouncing back of light from a surface is called __________.
Answer: reflection
2.
The angle of incidence is equal to the angle of __________.
Answer: reflection
3.
The centre of a spherical mirror’s reflecting surface is called its __________.
Answer: pole
4.
The centre of the sphere of which a spherical mirror forms a part is called the __________.
Answer: centre of curvature
5.
The distance between the pole and focus is called __________.
Answer: focal length
6.
For a spherical mirror, (R=) __________.
Answer: (2f)
7.
A mirror with its reflecting surface curved inward is called a __________ mirror.
Answer: concave
8.
A mirror with its reflecting surface curved outward is called a __________ mirror.
Answer: convex
9.
A convex mirror always forms a __________, __________ and __________ image.
Answer: virtual, erect, diminished
10.
A concave mirror can form both __________ and __________ images.
Answer: real, virtual
11.
The mirror formula is (\frac1v+\frac1u=) __________.
Answer: (\frac1f)
12.
The magnification of a spherical mirror is (m=) __________.
Answer: (-v/u)
13.
The change in direction of light when it enters another transparent medium is called __________.
Answer: refraction
14.
When light travels from a rarer to a denser medium, it bends __________ the normal.
Answer: towards
15.
When light travels from a denser to a rarer medium, it bends __________ the normal.
Answer: away from
16.
The law (\sin i/\sin r=\text{constant}) is called __________.
Answer: Snell’s law
17.
The speed of light in vacuum is approximately __________.
Answer: (3\times10^8,m/s)
18.
The refractive index of a medium is (n=) __________.
Answer: (c/v)
19.
In a rectangular glass slab, the emergent ray is __________ to the incident ray.
Answer: parallel
20.
A convex lens is also called a __________ lens.
Answer: converging
21.
A concave lens is also called a __________ lens.
Answer: diverging
22.
The central point of a lens is called its __________.
Answer: optical centre
23.
A ray passing through the optical centre of a lens emerges without __________.
Answer: deviation
24.
The focal length of a convex lens is __________ according to the sign convention.
Answer: positive
25.
The focal length of a concave lens is __________ according to the sign convention.
Answer: negative
26.
The lens formula is (\frac1v-\frac1u=) __________.
Answer: (\frac1f)
27.
The power of a lens is the __________ of its focal length.
Answer: reciprocal
28.
The SI unit of lens power is __________.
Answer: dioptre
29.
The power of a convex lens is __________.
Answer: positive
30.
The power of a concave lens is __________.
Answer: negative
D. True or False
1.
The image formed by a plane mirror is real.
False
2.
A plane mirror produces lateral inversion.
True
3.
A concave mirror always produces a virtual image.
False
4.
A convex mirror always produces a diminished image.
True
5.
A convex mirror has a wider field of view than a plane mirror.
True
6.
The focal length of a concave mirror is positive under the New Cartesian convention.
False
7.
The focal length of a convex mirror is positive.
True
8.
Light bends towards the normal when it enters a denser medium obliquely.
True
9.
Light travels at the same speed in all transparent media.
False
10.
The emergent ray from a rectangular glass slab is parallel to the incident ray.
True
11.
A convex lens is a diverging lens.
False
12.
A concave lens always forms a virtual, erect and diminished image.
True
13.
A ray through the optical centre of a lens suffers significant deviation.
False
14.
The power of a concave lens is negative.
True
15.
Lens power is measured in metres.
False
16.
A shorter focal length means greater lens power.
True
E. Match the Following
Set 1
| Column A | Column B |
|---|---|
| 1. Concave mirror | a. Diverging lens |
| 2. Convex mirror | b. Converging lens |
| 3. Convex lens | c. Converging mirror |
| 4. Concave lens | d. Diverging mirror |
Answers:
1–c, 2–d, 3–b, 4–a
Set 2
| Column A | Column B |
|---|---|
| 1. Pole | a. (c/v) |
| 2. Refractive index | b. Centre of reflecting surface |
| 3. Power | c. (1/f) |
| 4. Mirror magnification | d. (-v/u) |
Answers:
1–b, 2–a, 3–c, 4–d
Set 3
| Column A | Column B |
|---|---|
| 1. Convex mirror | a. Always virtual, erect, diminished |
| 2. Concave lens | b. Can give virtual enlarged image |
| 3. Concave mirror with object between P and F | c. Converging lens |
| 4. Convex lens | d. Always virtual, erect, diminished |
Answers:
1–a, 2–d, 3–b, 4–c
F. Very Short Answer Questions
1.
State the two laws of reflection.
2.
What is a spherical mirror?
3.
Define pole of a spherical mirror.
4.
What is the centre of curvature?
5.
Define focal length of a spherical mirror.
6.
Write the relation between (R) and (f).
7.
What is magnification?
8.
Write the mirror formula.
9.
Why is a convex mirror used as a rear-view mirror?
10.
Define refraction of light.
11.
What happens to light when it passes from a rarer to a denser medium?
12.
State Snell’s law.
13.
Define refractive index.
14.
Write the expression for absolute refractive index.
15.
What happens to the emergent ray after passing through a rectangular glass slab?
16.
What is a convex lens?
17.
What is a concave lens?
18.
Define optical centre of a lens.
19.
What is the focal length of a lens?
20.
State the lens formula.
21.
Write the expression for lens magnification.
22.
Define power of a lens.
23.
What is one dioptre?
24.
What is the sign of the power of a convex lens?
25.
What is the sign of the power of a concave lens?
G. Short Answer Questions
1.
Differentiate between a concave mirror and a convex mirror.
2.
Why can a concave mirror form both real and virtual images?
3.
Explain why a convex mirror is suitable for rear-view mirrors.
4.
Write the image characteristics when an object is placed between the pole and focus of a concave mirror.
5.
State the New Cartesian Sign Convention for spherical mirrors.
6.
Explain the meaning of positive and negative magnification for a spherical mirror.
7.
Why does a ray bend when it passes from one transparent medium to another?
8.
Explain the bending of light when it travels:
- from air to glass
- from glass to air.
9.
What is the difference between optical density and ordinary mass density?
10.
Explain why the emergent ray from a rectangular glass slab is parallel to the incident ray.
11.
Differentiate between convex and concave lenses.
12.
Why is a convex lens called a converging lens?
13.
Why is a concave lens called a diverging lens?
14.
Describe the three standard rays used to draw lens ray diagrams.
15.
Why does a concave lens always form a virtual, erect and diminished image?
16.
Describe the image formed by a convex lens when the object is:
- beyond (2F)
- at (2F)
- between (F) and (2F)
- between (F) and O.
17.
What is meant by the power of a lens? How is it related to focal length?
18.
Why must focal length be expressed in metres when calculating power?
19.
Explain the significance of the sign of lens power.
20.
What happens to the power of a lens when its focal length decreases?
H. Give Reasons
1.
A convex mirror is used as a rear-view mirror.
2.
A concave mirror can be used as a shaving mirror.
3.
Dentists use concave mirrors.
4.
A concave mirror is used in a solar furnace.
5.
A convex mirror can show a large area behind a vehicle.
6.
A pencil partially immersed in water appears displaced.
7.
Light bends when it enters glass from air.
8.
A ray bends away from the normal while moving from glass to air.
9.
The emergent ray from a rectangular glass slab is parallel to the incident ray.
10.
A concave lens is called a diverging lens.
11.
A convex lens is called a converging lens.
12.
A concave lens always forms a diminished image.
13.
A shorter focal length lens has greater power.
14.
A convex lens has positive power while a concave lens has negative power.
I. Ray Diagram Questions
Draw neat, labelled ray diagrams wherever required.
1.
Draw the image formation by a concave mirror when the object is:
- beyond C
- at C
- between C and F
- between F and P.
2.
Draw the ray diagram for an object placed at infinity in front of a concave mirror.
3.
Draw the ray diagram showing image formation by a convex mirror for an object at a finite distance.
4.
Draw a ray diagram showing why a convex mirror produces a diminished image.
5.
Draw the ray diagram for a convex lens when the object is:
- beyond (2F_1)
- at (2F_1)
- between (F_1) and (2F_1)
- at (F_1)
- between (F_1) and O.
6.
Draw the ray diagram for a concave lens.
7.
Draw a labelled diagram showing refraction through a rectangular glass slab.
8.
Draw and label:
- incident ray
- normal
- refracted ray
- angle of incidence
- angle of refraction.
J. Numerical Questions — Mirrors
1.
A spherical mirror has radius of curvature (40,cm). Find its focal length.
2.
A concave mirror has focal length (15,cm). Find its radius of curvature.
3.
An object is placed (20,cm) in front of a concave mirror of focal length (10,cm). Find the image distance.
4.
An object (5,cm) high is placed (20,cm) in front of a concave mirror of focal length (10,cm). Find:
- image distance
- magnification
- image height
- nature of image.
5.
An object is placed (10,cm) in front of a convex mirror having focal length (15,cm). Find the image position and state its nature.
6.
A (5,cm) tall object is placed (20,cm) in front of a convex mirror of radius (30,cm). Find:
- image position
- magnification
- image height
- nature of image.
7.
An object is placed (27,cm) in front of a concave mirror of focal length (18,cm). Find the position, size and nature of the image.
8.
A mirror produces magnification (-2). What does the sign and magnitude tell you about the image?
K. Numerical Questions — Refraction
1.
The speed of light in vacuum is (3\times10^8,m/s). If its speed in a transparent medium is (2\times10^8,m/s), calculate the refractive index.
2.
A medium has refractive index (1.5). Calculate the speed of light in it.
3.
A ray travels from air into a transparent medium. If (i=45^\circ) and (r=30^\circ), calculate the refractive index using Snell’s law.
4.
The refractive index of a material is 2.0. What does this tell you about the speed of light in that material compared with vacuum?
5.
Light travels from medium A to medium B. Its speed changes from (3\times10^8,m/s) to (2\times10^8,m/s). Calculate the refractive index of B with respect to A.
L. Numerical Questions — Lenses
1.
Find the power of a convex lens of focal length (50,cm).
2.
Find the power of a concave lens of focal length (25,cm).
3.
A lens has power (+2D). Find its focal length and identify the type of lens.
4.
A lens has power (-2.5D). Find its focal length and identify the type of lens.
5.
An object is placed (15,cm) from a convex lens of focal length (10,cm). Find the image position.
6.
A (2,cm) tall object is placed (15,cm) in front of a convex lens of focal length (10,cm). Find:
- image distance
- magnification
- image height
- nature of image.
7.
A concave lens has focal length (15,cm) and forms an image (10,cm) from the lens. Find the object distance and magnification.
8.
A convex lens forms a real image at (50,cm) from the lens. The image is equal in size to the object. Find the focal length and power of the lens.
9.
Two lenses of powers (+2D) and (+3D) are placed in contact. Find the combined power.
10.
Two lenses of powers (+4D) and (-1.5D) are placed in contact. Find the net power.
M. Case-Based / Competency Questions
Case 1 — Rear-view Mirror
A driver uses a convex mirror on the side of a vehicle. The mirror forms an image of vehicles behind the car.
Questions
a. What type of image is formed?
b. Is the image larger or smaller than the object?
c. Why is this mirror preferred over a plane mirror?
d. Where is the image formed relative to the mirror?
Answers:
a. Virtual and erect
b. Smaller/diminished
c. It provides a wider field of view
d. Behind the mirror, between P and F.
Case 2 — Convex Lens
An object is placed between (F_1) and (2F_1) of a convex lens.
Questions
a. Where is the image formed?
b. Is it real or virtual?
c. Is it erect or inverted?
d. Is it enlarged or diminished?
e. Draw the ray diagram.
Answers:
a. Beyond (2F_2)
b. Real
c. Inverted
d. Enlarged
Case 3 — Rectangular Glass Slab
A ray of light is incident obliquely on a rectangular glass slab.
Questions
a. What happens when the ray enters glass?
b. What happens when it leaves glass?
c. What is the direction of the emergent ray compared with the incident ray?
d. Name the phenomenon involved.
Answers:
a. It bends towards the normal.
b. It bends away from the normal.
c. It is parallel to the incident ray.
d. Refraction.
Case 4 — Lens Power
An optician prescribes a lens of power (+1.5D).
Questions
a. Is the lens convex or concave?
b. Is it converging or diverging?
c. Calculate its focal length.
d. What is the sign of its focal length?
Answers:
a. Convex
b. Converging
c. (f=1/1.5\approx0.67m)
d. Positive
N. HOTS / Conceptual Questions
1.
A student says, “A convex mirror cannot form an image because it diverges light.” Is the statement correct? Explain.
2.
A concave mirror produces a virtual, erect and enlarged image. Where must the object be placed?
3.
Why does a convex mirror allow a driver to see more area behind the vehicle?
4.
Can a concave mirror produce an image smaller than the object? Give the required object position.
5.
Can a convex lens produce a virtual image? If yes, where should the object be placed?
6.
Can a concave lens form a real image of a real object under the conditions studied in this chapter? Explain.
7.
Two lenses have the same focal length magnitude, but one is convex and the other concave. How will their powers differ?
8.
Two lenses have powers (+2D) and (-2D). What will be their combined power when placed in contact?
9.
Why is the sign of focal length important while solving numerical problems?
10.
A student uses centimetres directly in (P=1/f) and gets an incorrect unit. Explain the mistake.
11.
If the refractive index of a medium increases, what does this indicate about the speed of light in that medium?
12.
Why does a ray passing through the optical centre of a thin lens emerge approximately undeviated?
O. Important “Compare and Differentiate” Questions
1.
Differentiate between:
- real image and virtual image.
2.
Differentiate between:
- concave mirror and convex mirror.
3.
Differentiate between:
- convex lens and concave lens.
4.
Differentiate between:
- reflection and refraction.
5.
Differentiate between:
- converging and diverging optical devices.
6.
Compare the image formed by:
- convex mirror
- concave lens.
7.
Compare the image formed by:
- concave mirror when object is between P and F
- convex lens when object is between O and F.
8.
Differentiate between focal length of a convex lens and focal length of a concave lens using the sign convention.
P. “Write the Formula” Questions
1.
Write the relation between radius of curvature and focal length of a spherical mirror.
2.
Write the mirror formula.
3.
Write the magnification formula for a spherical mirror.
4.
Write Snell’s law.
5.
Write the formula for refractive index in terms of speed of light.
6.
Write the lens formula.
7.
Write the magnification formula for a lens.
8.
Write the formula for power of a lens.
9.
Write the formula for combined power of lenses in contact.
Q. “Identify the Optical Device” Questions
1.
Which mirror is used as a vehicle rear-view mirror?
Answer: Convex mirror
2.
Which mirror can be used as a shaving mirror?
Answer: Concave mirror
3.
Which mirror is used in solar furnaces?
Answer: Concave mirror
4.
Which lens is used when convergence of light is required?
Answer: Convex lens
5.
Which lens causes divergence of parallel rays?
Answer: Concave lens
6.
Which optical device always produces a virtual, erect and diminished image?
Answer: Convex mirror / concave lens
7.
Which optical device can produce an enlarged virtual image?
Answer: Concave mirror or convex lens, for suitable object positions.
Important Questions for Examination
If you cannot solve the whole bank, do these first:
- State the laws of reflection.
- Explain the image formation by a concave mirror for different object positions.
- Explain why convex mirrors are used as rear-view mirrors.
- State the New Cartesian Sign Convention.
- Derive/use the mirror formula in numerical problems.
- Solve magnification problems for spherical mirrors.
- Explain refraction and the bending of light towards/away from the normal.
- State and apply Snell’s law.
- Define refractive index and relate it to speed of light.
- Explain refraction through a rectangular glass slab.
- Compare convex and concave lenses.
- Draw all important convex-lens ray diagrams.
- Explain why a concave lens always forms a virtual, erect and diminished image.
- Apply the lens formula to numerical problems.
- Calculate magnification produced by a lens.
- Calculate lens power from focal length.
- Calculate focal length from lens power.
- Solve questions involving combinations of lens powers.
- Practise sign-convention-based numericals.
- Practise case-based questions involving mirrors, lenses and refraction.
Formulae to Memorise Before Attempting Numericals
[
\boxed{R=2f}
]
[
\boxed{\frac1v+\frac1u=\frac1f}
]
[
\boxed{m=-\frac vu}
]
[
\boxed{n=\frac cv}
]
[
\boxed{\frac{\sin i}{\sin r}=n}
]
[
\boxed{\frac1v-\frac1u=\frac1f}
]
[
\boxed{m=\frac vu}
]
[
\boxed{P=\frac1f}
]
[
\boxed{P_{\text{total}}=P_1+P_2+\cdots}
]