UNIVERSITY OF CAGAYAN VALLEY

(formerly Cagayan Colleges Tuguegarao)

Victor V. Perez Campus, Tuguegarao City, Cagayan Valley, Philippines
SCHOOL OF LIBERAL ARTS AND TEACHER EDUCATION
Teaching Science in the Secondary Education
Academic Year 2024-2025

DETAILED
LESSON PLAN
in
Grade 12
(Law Of Refraction)

Submitted to: Mrs. Abigail Q. Fernandez

Submitted by: Jerickson Ruiz C. Ong
I. Objectives
At the end of the lesson, the students should be able to:
A. illustrate and identify the path of light rays as they are refracted;
B. define the law of refraction;
C. calculate the different refractive index of different medium; and
D. relate refraction to different light phenomena.
II. Subject Matter
A. Topic: Law of Refraction

B. References: : DepEd Physical Science Quarter 2 Module 3

Laws of reflection, Byjus.com

Total internal Reflection, Geeksforgeeks.org

C. Materials: Whiteboard, marker, water, pen, glass, television, and laptop, flashlight.
D. Values Integration: Applying law of refraction to understand concept in common light
phenomea.

III. Procedure
Teacher’s Activity Student’s Activity
A. Preliminary Activities
- Prayer
-Greetings
-Classroom Management
-Attendance

B. Motivation
Before we start our discussion in the topic, I have
prepared a simple observation that you will do. I
have here a glass of water and a pen. Observe
what will happen to the pen as I submerged it into
the water.

What do you notice about the appearance of the

pen where it enters the water? It looks bigger Sir

Does the pen appear bent or broken? Broken Sir

Why do you think this happens? Because of the water that makes the pen
looks bigger and broken Sir
What are the two-medium involved in this
observation? Water and Air Sir

How does the speed of light change when it

moves from air to water? It slows down Sir.

Yes, because of the higher density of water, the

speed of light slows down because the water
molecules are closer to one another, causing more
interaction than delay of light’s progress.

This scenario is what we call refraction.

Refraction of light occurs when there is a bending
of light when it passes from one material to
another, like from air to water.

C. Presentation

Have you ever experienced looking in a distance

during hot days and seeing a puddle of water in
the middle of the road? Yes Sir

Okay this is one application of refraction.

What do you call this phenomenon? Mirage Sir

Yes, mirage is an optical illusion caused by the

refraction of light due to temperature differences
in the air which makes distant object look distant,
displaced, or even creates the illusion of water on
roads.

Before we explain more about this concept, I

would like to share to you our lesson objective.
At the end of the lesson, the students
should be able to:
A. illustrate and identify the path of light
rays as they are refracted;
B. define the law of refraction;
C. calculate the different refractive index
of different medium; and
D. relate refraction to different light
phenomena.
Very good!
D. Discussion

Just like what we have stated earlier, refraction

occurs when there is a bending of light where
there are two medium involve. Like what we
have observed earlier using the pen and glass of
water, what are the two medium involved? Air and water Sir

Very Good! Using the observation earlier we will

now identify the rays and angles in refraction.
What is the two medium that you can see in the
illustration? Air and water Sir

Where do you find the incident ray? Above the boundary Sir

Yes this incident ray is the ray AO

What is the medium in that area? Air Sir

And how about the refracted ray? Bellow the boundary Sir

Okay and this is the ray OB

What is the medium in the refracted ray? Water Sir

Very Good!

Now there is a normal line in the middle of the

illustration, What is the angle that formed
between the incident ray and to the normal line? Angle of incidence Sir

How about the angle between the refracted ray

and normal line? Angle of refraction Sir

Excellent!

There is what we call the Law of Refraction.

What is this law? also known as Snell's Law, describes how
light bends when it passes from one
medium to another.

Very Good! What does it state? It states that:

1. The angle of incidence (θ₁) is the
angle between the incident ray and
the normal line (an imaginary line
perpendicular to the surface).
2. The angle of refraction (θ₂) is the
angle between the refracted ray
and the normal line.
Yes, The law relates the angles of incidence and
refraction to the refractive indices of the two
media involved. It is expressed mathematically
as:
n₁sin(θ₁) = n₂sin(θ₂)
Where:

n₁ is the refractive index of the first medium

n₂ is the refractive index of the second medium
θ₁ is the angle of incidence.
θ₂ is the angle of refraction.

So here are the refracted indices for some

common materials:
Material Refractive Index (n)
Air 1.003
Water 1.33
Glass 1.50
Diamond 2.42

What is the refracted indices of water? 1.33

How about the glass? 1.50

Very Good! Now let us try some sample problem

to find the refracted ray of this illustration.

In this illustration lets just say that the angle of

incidence is 30 degrees, what is the angle of the
refraction inside the glass?

So to solve this problem we have to identify first

the given.

What is our n1? Or the refractive index in the

first medium? 1.003 sir
How about our n2? Or the refractive of the
second medium? 1.33

And lastly what is the angle of the incidence?

30 Degrees
And what is the unknown?
Angle of reflection or ∅ 2
And now lets substitute the given.
n1 * sin(θ1) = n2 * sin(θ2)

1.00 * sin(30°) = 1.33 * sin(θ2)

Solve for θ2 (angle of refraction):

sin(θ2) = (1.00 * sin(30°)) / 1.33
sin(θ2) = 0.5
θ2 = arcsin(0.5) ≈ 22.02 degrees Answer: The angle of refraction inside the
glass is approximately 19.5 degrees.
very good class and now

lets try another solving

identify knowns:
n1 (index of refraction of air) = 1.00
n2 (index of refraction of glass) = 1.50
θ1 (angle of incidence) = 30 degrees

Apply Snell's Law:

n1 * sin(θ1) = n2 * sin(θ2)
-1.00 * sin(30°) = 1.50 * sin(θ2)

Solve for θ2 (angle of refraction):

sin(θ2) = (1.00 * sin(30°)) / 1.50
sin(θ2) = 0.333
θ2 = arcsin(0.333) ≈ 19.5 degrees

Answer: The angle of refraction inside the glass

is approximately 19.5 degrees.

Do you understand class?

Yes Sir
Do you have any questions?
None sir
Now lets have a short trivia about refraction

Do you have any idea where a refraction occur?

Rainbows Sir
 Rainbows appear when sunlight
passes through raindrops.
 The light bends and splits into
different colors because each color
travels at a slightly different speed
in water.
In Mirages on Hot Roads or in Deserts Sir
 On hot days, you might see what
looks like water on the road—but
when you get closer, it disappears!
 This is because hot air near the
ground bends light from the sky,
making it look like a reflection of
water.
In Glasses and Contact Lenses Sir
 People who wear glasses or
contacts use lenses that bend light
 to help their eyes focus better.
 This works by changing the way
light enters the eye, correcting
vision problems.
In Cameras and Projectors sir
 Cameras use lenses to focus light
onto a sensor to create sharp
images.
Excellent class.  Projectors bend and direct light to
display large images on a screen.

E. Generalization
Lets have a short recap a bending of light where there are two
refraction occurs when there is? medium involve Sir

Thank you

Can a refraction occur when there is only one no Sir

medium?
incident and refracted ray Sir
What are the two kind of Ray’s again?

Very Good! Class look like you’re all ready for

activity.

F. Application
"Refraction through Different Materials"
Group your self into 5
Objective:
To explore how light behaves when passing
through various transparent materials.
Materials Needed:
 A flashlight
 A protractor
 Different transparent objects (glass, water
bottle, plastic, glass plate, etc.)
Instructions:
1. Shine the Flashlight:
Shine a flashlight at a specific angle
through the first transparent object (e.g., a
glass plate) and measure the angle of
refraction.
2. Change the Object:
Have students repeat the experiment with
other transparent objects (water bottle,
plastic, etc.), and compare how the angle
of refraction changes.
3. Record Observations:
Use a protractor to measure the angles of
refraction for each object and have
students note down how the refraction
changes depending on the material. Yes Sir

Understand the instruction class?

 Additional questions for the activity:

Before the Experiment:

1. What do you think will happen when light
passes through different transparent
materials?
2. Why do you think light bends when it
enters a new medium?
3. How do you think the density of a
material affects the angle of refraction?
During the Experiment:
4. Did the light bend the same way for all
materials? Why or why not?
5. Which material caused the light to bend
the most? The least?
6. How does the angle of the incident light
affect the angle of refraction?
After the Experiment:
7. How can this experiment be applied to
real-life situations (e.g., eyeglasses,
camera lenses, or optical fibers)?
8. What role does the refraction index of a
material play in refraction?
9. How would refraction behave if we used a
liquid (like oil or alcohol) instead of a
solid material?
10. If we used a colored light instead of white
light, do you think the bending would be
the same? Why or why not? Yes Sir
(students do the activity)
Do you understand the instruction class?

G. Valuing
Solve the following
1. Light travels from a medium with a
refractive index of 1.2 into a medium with
a refractive index of 1.8. The angle of
incidence is 25°. What is the angle of
refraction?
2. Two transparent materials are in contact.
Material A has a refractive index of 1.5,
and Material B has a refractive index of
1.7. Light is incident from Material A to
Material B at an angle of 35°. What is the
angle of refraction in Material B?
3. A light ray passes from a medium with
refractive index 1.6 to another medium
with refractive index 1.2. If the angle of
incidence is 20°, what is the angle of
refraction?
IV. Evaluation
Multiple Choice Quiz: Law of Refraction
Direction: Encircle the best answer in each question. (Each question is worth 1 point)
1. What does the Law of Refraction (Snell's Law) describe?
A) The reflection of light from a surface
B) The bending of light as it passes from one medium to another
C) The scattering of light in all directions
D) The absorption of light in a medium
Answer: B) The bending of light as it passes from one medium to another

2. Which equation represents Snell’s Law?

A) n1⋅sin⁡(θ1)=n2⋅sin⁡(θ2)n_1 \cdot \sin(\theta_1) = n_2 \cdot \sin(\theta_2)n1⋅sin(θ1)=n2⋅sin(θ2)
B) n1+n2=sin⁡(θ1)+sin⁡(θ2)n_1 + n_2 = \sin(\theta_1) + \sin(\theta_2)n1+n2=sin(θ1)+sin(θ2)

⋅cos(θ2)
C) n1⋅cos⁡(θ1)=n2⋅cos⁡(θ2)n_1 \cdot \cos(\theta_1) = n_2 \cdot \cos(\theta_2)n1⋅cos(θ1)=n2

D) n1/n2=θ1/θ2n_1 / n_2 = \theta_1 / \theta_2n1/n2=θ1/θ2

Answer: A) n1⋅sin⁡(θ1)=n2⋅sin⁡(θ2)n_1 \cdot \sin(\theta_1) = n_2 \cdot \sin(\theta_2)n1⋅sin(θ1
)=n2⋅sin(θ2)

3. If light moves from a less dense medium (lower refractive index) to a denser medium (higher
refractive index), how does the light bend?
A) Away from the normal
B) Towards the normal
C) It does not bend at all
D) It bends randomly
Answer: B) Towards the normal

4. Which of the following materials has the highest refractive index?

A) Air
B) Water
C) Glass
D) Diamond
Answer: D) Diamond

5. A light ray travels from air (n = 1.00) into water (n = 1.33) at an incident angle of 30°. What
happens to the speed of light in water?
A) It increases
B) It decreases
C) It stays the same
D) It depends on the wavelength of light
Answer: B) It decreases

6. A light ray passes from water (n = 1.33) into air (n = 1.00) at an angle of 50°. What will
happen if the angle of incidence keeps increasing?
A) The light will refract at a smaller angle
B) The light will refract at a greater angle
C) The light will undergo total internal reflection
D) The light will stop traveling
Answer: C) The light will undergo total internal reflection

7. What is the critical angle?

A) The angle at which no refraction occurs
B) The angle of incidence that results in an angle of refraction of 90°
C) The angle at which light completely passes through a medium
D) The angle at which total absorption of light happens
Answer: B) The angle of incidence that results in an angle of refraction of 90°

8. If a light ray enters a medium at a 0° angle (perpendicular to the surface), what will happen?
A) The light will bend toward the normal
B) The light will bend away from the normal
C) The light will continue in a straight line without bending
D) The light will be completely absorbed
Answer: C) The light will continue in a straight line without bending

9. A pencil appears bent when placed in a glass of water. Which phenomenon is responsible for
this?
A) Reflection
B) Refraction
C) Diffraction
D) Dispersion
Answer: B) Refraction

10. How does the wavelength of light change when moving from air to glass?
A) It increases
B) It decreases
C) It remains the same
D) It disappears
Answer: B) It decreases
V. Agreement
A. Follow-up
List at least 5 to 10 items that can be apply a refreaction in your household
B. Advance
Read about the lesson in