Science - Grade 10

REFLECTION OF LIGHT IN A PLANE MIRROR

I. INTRODUCTORY CONCEPT
A mirror is a fascinating piece of glass that we use on a daily basis. We
always look at it to see how presentable we are and sometimes we wonder how the
image was created. Plane mirrors are almost everywhere. It's typically made of glass
with a gleaming metal backing that reflects all light that hits it. When a mirror reflects
light, an image is formed. An image is a reflection-created copy of an object.

We are aware that a mirror is a reflective surface that reflects light. Light
reflected by one mirror can easily be reflected by another, and so on. When two
mirrors are held at an angle and an object is placed in between the mirrors, multiple
images are formed due to reflection from one mirror to the other.

II. LEARNING COMPETENCIES

Predict the qualitative characteristics (orientation, type, and magnification) of images

formed by plane and curved mirrors and lenses. (S10FE-IIg-50)
Objectives:
1. Explain the law of reflection.
2. Compare the actual height, width, and the distance from the mirror of the
object with that of the image formed by the plane mirror.
3. Describe the image formed by plane mirror.
4. Identify the relationship between the number of images formed and the
angle between the two mirrors.
5. Find the number of images formed by two mirrors at a given angle between
them.
III. ACTIVITIES

ELICIT:

Let’s get started and let us see what you know about this lesson. Read each
statement carefully and write the letter that corresponds to the correct answer.

1. What happens when light strikes a smooth surface?

A. The light is polarized. C. The light is refracted
B. The light is reflected. D. The light is bent around corners.

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2. Which of these is the image in a plane mirror?
A. It is always erect but reversed.
B. It is always erect but not reversed.
C. It is always inverted but reversed.
D. It is always inverted but not reversed.

3. What kind of image is formed by a plane mirror?

A. real image C. multiple image
B. virtual image D. none of these

4. Which of these is NOT the property of an image formed by a plane mirror?

A. The image is erect.
B. The image obtained is virtual.
C. The image is laterally inverted.
D. The size of the image is smaller than the size of the object.

5. When an object's image is seen in a plane mirror, what determines the distance
between the mirror and the image?
A. the size of the image
B. the wavelength of light used for viewing
C. the distance from the object to the mirror
D. the distance of both the observer and the object to the mirror

6. How many images will be formed if two plane mirrors will be placed at 30o angle?
A.10 B.11 C. 12 D.13

7. At what angle will the two plane mirrors form a single image?
A.60o B. 70o C. 90o D. 180o

8. What is the formula for finding the number of images formed by two plane mirrors?
A. N= (360 + angle between the mirrors) – 1
B. N = (360- angle between the mirrors) + 1
C. N = (360 x angle between the mirrors) – 1
D. N = (360/ angle between the mirrors) – 1

9. What law states that angle of incidence is equal to the angle of reflection?
A. Charles’ Law C. Law of Acceleration
B. Law of Inertia D. Law of Reflection

10. If you stand three feet in front of a plane mirror, how far away would you
see your image from the mirror ?
A. 1.5 ft B. 3 ft C. 6 ft D. 12 ft

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ENGAGE:
Activity 1: MIRROR, MIRROR ON THE WALL

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ectioninmirrorvector9533017&psig=AOvVaw0sf1U0rugutkwq
XFw5t0n&ust=1629117550716000&source=images&cd=vfe&
ved=0CAsQjRxqFwoTCOjI9IGGs_ICFQAAAAAdAAAAABAI

Instruction: Stand in front of a plane mirror.

1. Is there a reflection of light in the mirror? ___________
2. What did you see when you look at the mirror? ___________
3. Is your image exactly the same in size as you are___________
4. Raise your right hand. What hand does your image raise? _________
5. Is your image erect or inverted? ___________
6. Is it real or virtual? _______

Activity 2: MEASURING ANGLES

Direction: Using a protractor measure the angle between mirror 1 and mirror 2 and
write it on the blank.

1. 2.
:

Mirror 1 Mirror 1

Mirror 2 Mirror 2
_______________ _______________

3. 4.
Mirror 1 Mirror 1

Mirror 2 Mirror 2
_______________ _______________

5. 6.
Mirror 1 Mirror 1

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 Mirror 2
Mirror 2

_______________ _______________

EXPLORE:

Activity 1: MY IMAGE AND ME

Directions: Analyze the nature of image formed by a plane mirror and answer
the questions below.

Source: CBSE,”Nature of Image Formed by a

Plane Mirror-Light”, December22,2015, Retrieved from
https://www.youtube.com/watch?v=Poq3u7BFhqk

1. What is the size of image formed by a plane mirror?

_______________________________________________________________________
_______________________________________________________________________

2. What type of image is formed by plane mirrors?

_______________________________________________________________________
_______________________________________________________________________

3. Where is the image of the object in a plane mirror?

_______________________________________________________________________
_______________________________________________________________________

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4. Compare the distance of the man to the mirror and the distance of his image
from the mirror.
_______________________________________________________________________
_______________________________________________________________________

Activity 2: MULTIPLE IMAGES

Study the given example and perform the activity below using the given formula to
determine the number of images that will be formed by two plane mirrors with a
given angle between them.

Given: angle between two mirrors = 600

Required: Number of images

Solution:
formula : N= ____3600_____________ - 1
angle between the mirrors
N = 3600 - 1
600
N= 6–1
N = 5 images

Direction: Using the equation below, find the number of images that will be formed by
the two plane mirrors with a given angle between them. Show your solution.

N= ________3600_____________ - 1
angle between the mirrors

Table: Number of Images Formed

Angles Number of Images

0
1. 10
2. 240
3. 400
4. 900
5. 1200
6. 1800

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 1. Solution: 4. Solution:

2. Solution: 5. Solution:

3. Solution: 6. Solution:

Activity 3: THE ANGLE BETWEEN US

Find the angle between two mirrors that produced the given number of
images. Show your solution.

Note: Use this equation to find the angle.

angle between the mirrors = ______3600_______

number of images +1

Number of images Angle between the mirrors

1. 5

2. 7

3. 11

4. 14

5. 35

6. 39

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 1. Solution 4. Solution

2.Solution 5. Solution

3. Solution 6. Solution

EXPLAIN

REFLECTION OF LIGHT IN MIRRORS

When light hits a smooth surface, light is reflected, and an image is formed.
An image is a copy of an object formed by reflection. Reflection is the bouncing off
of light rays when it hits a surface like a plane mirror. When we look at a mirror or
any polished metal or a still pool of water, we can see our images because these
objects are image reflecting objects.

There are two types of images formed by reflecting surfaces. They are real
and virtual images. Real image is always inverted and is formed by actual rays of
light. It appears in front of the mirror and can be projected on the screen. Virtual
image is always erect and formed by apparent rays of light. Virtual image appears
behind the mirror.

Properties of an Image Formed by Plane Mirror

 The image formed is virtual.
 The image is erect.
 The size of the image is same as the size of the object.
 The distance between the image obtained is same as the distance
between the object from the mirror.

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Reflection of Light/Class 8, Light .Retrieved from
https://www.google.com/search?q=free+image+of+law+of+reflection&tbm=isch&chips=q:free+image+of+law+of+reflection,online_chips:i
ncident&hl=en&ve

The ray of light approaching the mirror represented by an arrow pointing

towards the mirror is called incident ray. This incident ray touches the mirror, and
the mirror sends this ray of light back. The ray of light which leaves the mirror and is
represented by an arrow pointing away from the mirror is called the reflected ray.

An imaginary line that can be drawn perpendicular to the surface of the mirror
is the normal line. The angle formed between the incident and normal is called angle
of incidence and the angle formed between the reflected ray and normal is called
angle of reflection. The angle of incidence and reflection are always measured from
the normal and not from the mirror. If the angle of incidence is 300 then the angle of
reflection will also be 300. Reflection of light follows the laws of reflection.

LAWS OF REFLECTION

Angle of incidence is equal to the angle of reflection.

The incident ray, normal and the reflected ray all lie in the same plane

Source: Henderson,2019,”The Law of Reflection”,

. Retrieved from https://www.physicsclassroom.
com/class/refln/Lesson-1/The –Law of Reflection

MULTIPLE IMAGES

Multiple images are

the images that are formed when
two or more mirrors are placed in
front of each other, and an object
is placed between them.
Two Mirrors Placed at Angle, Retrieved from
https://www.google.com/search?q=multiple+images+in+front+of+two+mirrors&so
urce=lnms&tbm=isch&sa=X&ved=2ahUKEwjl1r- fqJ_qAhWWwosBHdzaAg0Q_A

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 When two mirrors are kept at an angle and an object is placed in between the
mirrors, multiple images are formed due to reflection from one mirror on to the
other.

 The number of images of the object formed depends on the angle between
the two mirrors.

 The number of reflected images increases or decreases with the increasing or

decreasing of angle between them.

 As the angle between the mirrors decreases the number of images formed
increases.

 When the mirrors are facing each other and parallel, there will be infinite
images

 The number of images can be determined using the formula below

N= ________3600_____________ - 1
angle between the mirrors

ELABORATE:
Answer the following questions:

1. What changes did you notice on the number of images as the angle increased?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2. What is the relationship between the number of formed images and the angle
between two mirrors?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________

EXTEND:

Complete the following tasks to expand on what you've learned:

A. If you have available plane mirrors at home, try placing them at the following
angles and counting the number of images that result.

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  600 ___________________________
 450 ___________________________
 1800___________________________
 900___________________________
 1200___________________________

B. What will you do if you want to see more images from the mirrors?
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________

EVALUATION

A. Direction: Analyze the images provided below and respond to the questions that
follow.
A. B.

Demonstration Mirror, Concave. Retrieved Who’s that handsome cat? Retrieved

fromhttps://www.pasco.com/products/lab-apparatus/light- from https://cheezburger.com/6572917760
and-optics/ray-optics/se-7573

1. Which of the given pictures show an image on a plane mirror? _________

2. Which of the mirrors has an image that is erect and virtual? _________

3. Consider the diagram below. Which one of the angles (A, B, C, or D) is the angle
of incidence? _________ Which one of the angles is the angle of
reflection? _________

https://www.physicsclassroom.com/class/refln/Lesson-1/The-Law-of-Reflection

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 4. A ray of light is incident towards a plane mirror at an angle of 30-degrees with
the mirror surface.
What will be the angle of reflection? __________________
What will be the angle of incidence?__________________


https://www.physicsclassroom.com/class/refln/Lesson-1/The-Law-of-Reflection

5. What is the relationship between the angles of incidence and reflection?

_____________________________________________________

B. Read each statement carefully and choose the letter that corresponds to the
correct answer. Write the letter of the answer on the space before each number.

____1. What is the angle at which the two plane mirrors will form 8 images?
A. 400 C. 600
B. 500 D. 800
____2. What happens to the number of images as the angle between the mirror
decreases?
A. decreases C. increases
B. doubles D. remain the same

____3. How many plane mirrors are needed to produce multiple images ?

A. 1 B. 2 C. 3 D .4

____ 4. How many images would be formed if you held the mirrors at 180 degrees?
A. 1 B. 2 C.3 D. 4

____5. All of these are properties of an image formed by a plane mirror except
A. The image is erect.
B. The image obtained is virtual.
C. The size of the image is bigger than the size of the object
D. The distance between the image obtained is same as the distance
between the object from the mirror.

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 IV. RUBRIC FOR SCORING
Problem Solving (applicable in all problem solving)

5 4 3 2
The computations Most of the Some of the Little to none of
are all correct. computations are computations are the computation
correct correct is correct.

V. REFLECTION

I have learned that_______________________________________________

________________________________________________________________
________________________________________________________________
________________________________________________________________

I wish to ask my teacher about:

_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________

VI. ANSWER KEY

Elicit
1. B ENGAGE
2. A Activity 1: MIRROR, Activity 2: Measuring
3. B MIRROR ON THE WALL Angles
4. D 1. 900
5. C 1. Yes 2. 450
6. B 2. my own image
3. 800
7. D 3. YES
8 .D 4. the left hand 4. 300
9. C 5. erect 5. 1250
10. B 6.virtual 6. 1800

Explore

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 Activity 1: My Image and Me Activity 2. Activity 3.
1. the same size as the object Multiple Images The Angle Between
2.virtual image 1. 35 Us
3. behind the mirror 2. 14 1. 600
4.The distance of the man from the 3. 8 2. 450
mirror is the same as the distance of 4. 3 3. 300
his image from the mirror. 5. 2
6. 1 4. 240
5. 100
6. 90

Explain Extend
( Answers may vary) A. B. Answers may vary
1. 5
2. 7
3. 1
4. 3
5. 2
EVALUATION (A) 5. The angle of reflection is equal
1.B to the angle of reflection
2.B EVALUATION (B)
3.The angle of incidence is angle 1.A
2.C
C angle B is the angle of reflection.
3.B
4 . 600 4.A
600 5.C

VII. REFERENCES:

Acosta, H.,Alvarez,L., Angeles,D., Arre,R.,Carmona,M., Garcia,A., Gatpo,A.,

Marcaida, M., Olarete, M., Rosales,M., Salazar,N.(2015). Science 10 Learner’s
Material.Philippines: Department of Education.

Multiple Images retrieved from

https://www.google.com/search?q=multiple+images&oq=MULTIPLE+&aqs=chr
ome.2.69i59l3j0j69i57j69i60l3.11044j1j4&sourceid=chrome&ie=UTF-8

Physics Tutorial: The Law of Reflection - The Physics Classroom. Retrieved from
https://www.physicsclassroom.com/class/refln/lesson-1/the-law-of-reflection

Mirrors | Boundless Physics: Mirror. Retrieved from

https://courses.lumenlearning.com/boundless-physics/chapter/mirrors/

Plane Mirror: Characteristics of Images-mirrors. Retrieved from

https://byjus.com/physics/plane-mirrors/

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Writer:

CECILIA V. SADANG - Teacher I

San Pedro National High School
SDO, Iriga City

Reviewers:

HELEN Z. CORNELIO - EPS Science, Iriga City

MANUEL LUIS F. TEODORO - EPS Science, Masbate Province
MARNEL M. BULLO - Teacher III, Cataingan NHS
ELENITA P. FABELLA - Master Teacher II, Palanas North CS

Editors:

LOURDES P. CASTROVERDE - HT-III, Science, Zeferino Arroyo High School

MARISOL D. ANDRADA- Master Teacher, Sto. Niño National High School

Layout Artist:

RAYMOND T. TORALDE - Teacher II

Rinconada National Technical Vocational School - Annex

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