Interactive Physics Game

Light Reflection Ray Challenge

A light ray strikes a mirror and changes direction. Your mission is to identify the incident ray, locate the normal, compare the angles and predict the path of the reflected ray.

Your mission: Follow the rays carefully, solve five reflection cases and become a certified ray-tracing detective.

Scientific diagram showing an incident light ray, reflected ray, normal line and angles at a surface


The mirror follows the law even when nobody is watching.

Eye safety: Never shine a laser pointer, torch or reflected beam into anyone’s eyes. Classroom reflection activities should use a low-power torch under responsible adult or teacher supervision.

Meet the Parts of a Reflection Diagram

Incident Ray

The incident ray is the incoming light ray travelling towards the mirror.

Reflected Ray

The reflected ray is the light ray that leaves the mirror after reflection.

Normal

The normal is an imaginary line drawn at 90 degrees to the mirror at the point where the ray strikes.

Point of Incidence

This is the exact point where the incident ray reaches the reflecting surface.

Angle of incidence = Angle of reflection Both angles are measured from the normal, not from the surface of the mirror.
Diagram showing multiple rays reflecting from a flat plane mirror
Rays reflected by a plane mirror. Created by Fffred and released into the public domain. Source: Wikimedia Commons

Animated Ray Experiment

The red incident ray is already travelling towards the mirror. Activate the experiment to reveal the correct reflected ray.

Trace the light ray to the mirror
Normal
Incident ray
Reflected ray
35°
35°

The reflected ray is hidden. Predict its direction before revealing it. The reflected ray appears on the opposite side of the normal at the same angle. The incident angle is 35°, so the reflection angle is also 35°.

Light Reflection Challenge: Five Cases

Select the correct answer in each case. Your score updates automatically.

0 / 5 Current score
Case 1

A light ray strikes a mirror at an angle of incidence of 35°. What is the angle of reflection?

Correct! The angle of reflection equals the angle of incidence, so both angles are 35°.

Not quite. Measure both angles from the normal. The answer is 35°.

Case 2

What is the normal in a reflection diagram?

Correct! The normal is drawn at 90° to the mirror at the point of incidence.

Not quite. The normal is an imaginary perpendicular reference line.

Case 3

Which description identifies the incident ray?

Correct! The incident ray arrives at the reflecting surface.

Not quite. The incident ray travels towards the mirror. The outgoing ray is the reflected ray.

Case 4

Why can a simple periscope allow someone to see over an obstacle?

Correct! Light changes direction at the upper and lower reflecting surfaces before reaching the observer.

Not quite. A periscope redirects existing light using reflection.

Case 5

Which surface is most likely to form a clear reflected image?

Correct! A smooth mirror produces regular reflection, allowing a clear image to form.

Not quite. Rough surfaces scatter reflected rays in many directions, so they do not usually form clear images.

Reflection in a Periscope

Diagram comparing a simple periscope using two plane mirrors with a periscope using right-angled prisms
Diagram of simple periscopes by Tamasflex, licensed under Creative Commons Attribution-ShareAlike 3.0. Source and licence: Wikimedia Commons

How the Light Travels

Light from the object enters the top of the periscope and reflects from the upper mirror.

It then travels down the tube and reflects again from the lower mirror towards the observer’s eye.

Each reflection follows the same law: the angle of incidence equals the angle of reflection.

Three-Question Reflection Check

1. From which line are reflection angles measured?

Correct! Both angles are measured between the ray and the normal.

Not quite. Reflection angles are measured from the normal.

2. If the angle of incidence is 60°, what is the angle of reflection?

Correct! The two angles are equal, so the reflected angle is 60°.

Not quite. Apply the law of reflection: 60° in means 60° out.

3. What type of reflection occurs on a smooth mirror?

Correct! A smooth mirror produces regular reflection and can form a clear image.

Not quite. Smooth surfaces produce regular reflection.

Memory Challenge: Rebuild the Ray Diagram

Study these four terms. Close the section and try to place them correctly in an imaginary reflection diagram.

Incident ray
Reflected ray
Normal
Mirror
Correct arrangement: The incident ray travels towards the mirror. The normal passes through the point of incidence at 90° to the mirror. The reflected ray leaves on the other side of the normal at an equal angle.

Frequently Asked Questions

What is reflection of light?

Reflection is the change in direction that occurs when light strikes a surface and returns into the same medium.

What is the law of reflection?

The law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured from the normal.

What is the normal in a ray diagram?

The normal is an imaginary line drawn perpendicular to the reflecting surface at the point where the incident ray strikes it.

Why does a mirror form a clearer image than a wall?

A smooth mirror produces regular reflection, so reflected rays remain organised. A rough wall scatters rays in many directions and does not form a clear image.

How can students investigate reflection safely?

Students can use a small plane mirror, paper and a low-power torch under teacher supervision. Light, laser pointers and reflected beams must never be directed towards anyone’s eyes.

Speed Up Science 2.0
Follow the normal, compare the angles and the reflected ray will reveal its route.