Reflection

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Lesson notes

Key Facts about Light

Light is a **transverse wave**.
Transverse waves have vibrations **perpendicular** to the direction of wave travel.
Light travels at **300 000 000 m/s** (the speed of light).
Light is part of the **electromagnetic spectrum**, which contains seven types of transverse waves.

Specular Reflection

**Specular reflection** occurs when light reflects from a **very smooth surface**, like a mirror.
The **incident ray** is the ray approaching the surface.
The **normal** is an imaginary line drawn at **90°** to the surface.
The **angle of incidence** is the angle between the incident ray and the normal.
The **reflected ray** leaves the surface; its angle with the normal is the **angle of reflection**.
The **law of reflection** states: angle of incidence = angle of reflection.

Diffuse Reflection

**Diffuse reflection** happens when light reflects from a **rough surface**.
Rays are reflected at **many different angles** because the surface is uneven.
The law of reflection still holds for each individual ray (angle i = angle r).
The overall effect is that the reflected light is scattered, not focused.

The Law of Reflection

The law of reflection applies to **all waves**, not just light.
It can be stated as: **angle of incidence = angle of reflection**.
Both angles are measured from the **normal**, not from the surface.

Specular reflection showing incident ray, reflected ray, normal, and equal angles of incidence and reflection.

Slides

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Practice questions

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1.Which of the following best describes light?
Easy
- AA transverse wave
- BA longitudinal wave
- CA stationary wave
- DA mechanical wave
2.What is the speed of light?
Easy
- A300 000 000 m/s
- B300 000 m/s
- C3 000 000 m/s
- D30 000 000 m/s
3.The law of reflection states that:
Easy
- AThe angle of incidence equals the angle of reflection.
- BThe angle of incidence is greater than the angle of reflection.
- CThe angle of incidence is less than the angle of reflection.
- DThe angle of incidence is measured from the mirror surface.
4.Which type of reflection occurs when light hits a rough surface?
Medium
- ADiffuse reflection
- BSpecular reflection
- CTotal internal reflection
- DRegular reflection
5.In a specular reflection, the reflected rays are:
Medium
- AParallel to each other
- BScattered in many directions
- CAbsorbed by the surface
- DRefracted into the surface
6.What is the normal in a ray diagram?
Medium
- AA line drawn at 90° to the mirror
- BThe incident ray
- CThe reflected ray
- DThe mirror surface
7.Which of the following is true about diffuse reflection?
Hard
- AThe angle of incidence is still equal to the angle of reflection for each ray.
- BThe angle of incidence is not equal to the angle of reflection.
- CThe law of reflection does not apply.
- DThe surface is very smooth.
8.Which of the following waves obey the law of reflection?
Medium
- ALight waves only
- BAll waves
- COnly transverse waves
- DOnly electromagnetic waves

More questions

9.The diagram shows a ray of light incident on a mirror. The angle between the incident ray and the mirror is 30°. What is the angle of incidence?
Hard
- A60°
- B30°
- C90°
- D0°
10.In the diagram, what is the angle of reflection if the angle of incidence is 40°?
Hard
- A40°
- B50°
- C140°
- D0°
11.Which of the following surfaces would produce a specular reflection?
Easy
- AA calm lake
- BA piece of paper
- CA brick wall
- DA carpet
12.What is the direction of vibration in a transverse wave relative to the direction of wave travel?
Medium
- APerpendicular
- BParallel
- CAt 45°
- DRandom
13.A ray of light strikes a plane mirror at an angle of 30° to the mirror surface. What is the angle of incidence?
Medium
- A30°
- B60°
- C90°
- D45°
14.Which of the following surfaces would produce a diffuse reflection?
Easy
- AA polished mirror
- BA calm lake
- CA sheet of paper
- DA smooth metal plate
15.A light ray is incident on a mirror at an angle of 25° to the normal. What is the angle between the incident ray and the reflected ray?
Hard
- A25°
- B50°
- C75°
- D100°
16.Which of the following statements about the law of reflection is correct?
Medium
- AIt applies only to light waves.
- BIt applies to all waves.
- CIt applies only to transverse waves.
- DIt applies only to sound waves.
17.The diagram shows a ray of light reflecting from a mirror. The angle between the incident ray and the mirror is 40°. What is the angle of reflection?
Medium
- A40°
- B50°
- C80°
- D90°
18.What is the speed of light in a vacuum?
Easy
- A300 000 m/s
- B300 000 000 m/s
- C3 000 000 m/s
- D30 000 000 m/s
19.A student measures the angle of incidence and angle of reflection for a ray of light on a mirror. Which of the following sets of results would violate the law of reflection?
Hard
- AAngle of incidence = 30°, angle of reflection = 30°
- BAngle of incidence = 45°, angle of reflection = 45°
- CAngle of incidence = 0°, angle of reflection = 0°
- DAngle of incidence = 60°, angle of reflection = 30°
20.A ray of light is incident on a rough surface. What type of reflection occurs?
Medium
- ASpecular reflection
- BDiffuse reflection
- CTotal internal reflection
- DRefraction
21.In a ray diagram, the normal is drawn at what angle to the mirror?
Easy
- A0°
- B45°
- C90°
- D180°
22.Which of the following is an example of a transverse wave?
Medium
- ASound wave
- BLight wave
- CSeismic P-wave
- DLongitudinal wave in a spring
23.A ray of light is incident on a mirror at an angle of 35° to the normal. What is the angle between the incident ray and the mirror?
Medium
- A35°
- B55°
- C70°
- D90°
24.A student investigates reflection using a ray box and a plane mirror. She measures the angle of incidence as 30° and the angle of reflection as 29°. What is the most likely reason for this discrepancy?
Medium
- AThe law of reflection is not always obeyed.
- BThe mirror is not perfectly smooth.
- CThe student misread the protractor.
- DLight travels at different speeds in air.
25.A ray of light strikes a plane mirror at an angle of 20° to the mirror surface. What is the angle between the incident ray and the reflected ray?
Hard
- A40°
- B70°
- C140°
- D160°
26.Which of the following is a correct statement about specular reflection?
Easy
- AIt occurs on rough surfaces.
- BReflected rays scatter in many directions.
- CThe angle of incidence equals the angle of reflection for each ray.
- DIt only happens with light waves.
27.A student sets up an experiment to verify the law of reflection. She shines a ray of light at a mirror and measures the angles. Which of the following results would confirm the law?
Medium
- AAngle of incidence = 30°, angle of reflection = 30°
- BAngle of incidence = 30°, angle of reflection = 60°
- CAngle of incidence = 30°, angle of reflection = 150°
- DAngle of incidence = 30°, angle of reflection = 0°
28.A ray of light is incident on a plane mirror at an angle of 45° to the normal. The mirror is then rotated by 10° so that the normal also rotates by 10°. What is the new angle between the incident and reflected rays?
Hard
- A90°
- B100°
- C110°
- D120°
29.The diagram shows a ray of light reflecting from a plane mirror. The angle between the incident ray and the mirror is 25°. What is the angle of reflection?
Medium
- A25°
- B65°
- C75°
- D90°
30.In an experiment to investigate reflection, a student uses a ray box and a plane mirror. She places the mirror on a sheet of paper and draws the incident and reflected rays. Why is it important to mark the position of the mirror?
Medium
- ATo calculate the speed of light
- BTo draw the normal accurately
- CTo measure the wavelength
- DTo ensure the mirror is clean
31.A ray of light is incident on a mirror. The incident ray makes an angle of 30° with the mirror. If the mirror is rotated by 5° so that the angle of incidence increases by 5°, what is the new angle of reflection?
Hard
- A30°
- B35°
- C55°
- D65°
32.Which of the following is true about the normal in a ray diagram for reflection?
Medium
- AIt is drawn parallel to the mirror.
- BIt is drawn at 90° to the mirror.
- CIt is the same as the reflected ray.
- DIt is the path of the light ray.
33.A student performs an experiment to verify the law of reflection. She uses a protractor to measure angles. Which of the following could reduce the accuracy of her results?
Hard
- AUsing a sharp pencil to draw rays
- BEnsuring the mirror is vertical
- CReading the protractor from the side
- DUsing a ray box with a narrow slit
34.The diagram shows a ray of light incident on a plane mirror. Which labelled angle is the angle of incidence?
Medium
- AThe angle between the incident ray and the mirror
- BThe angle between the incident ray and the normal
- CThe angle between the reflected ray and the mirror
- DThe angle between the reflected ray and the normal
35.Which of the following best describes the normal in a ray diagram for reflection?
Easy
- AA line drawn perpendicular to the mirror at the point of incidence
- BA line drawn parallel to the mirror
- CA line drawn at 45° to the mirror
- DA line drawn along the incident ray
36.Light is an example of which type of wave?
Easy
- ATransverse wave
- BLongitudinal wave
- CMechanical wave
- DStanding wave
37.The speed of light in a vacuum is approximately:
Easy
- A300 000 000 m/s
- B300 000 m/s
- C3 000 m/s
- D300 m/s
38.Which of the following statements about diffuse reflection is correct?
Medium
- AIt occurs when light reflects from a rough surface, and the angle of incidence equals the angle of reflection for each ray.
- BIt occurs when light reflects from a smooth surface, and the angle of incidence equals the angle of reflection.
- CIt occurs when light reflects from a rough surface, and the angle of incidence is not equal to the angle of reflection.
- DIt occurs when light reflects from a smooth surface, and the angle of incidence is not equal to the angle of reflection.
39.A ray of light is incident on a plane mirror. The angle between the incident ray and the mirror is 40°. What is the angle of incidence?
Medium
- A50°
- B40°
- C90°
- D20°
40.Which of the following correctly describes the direction of vibration in a transverse wave?
Medium
- APerpendicular to the direction of wave travel
- BParallel to the direction of wave travel
- CIn the same direction as wave travel
- DCircular motion around the direction of wave travel

Revision notes

## Reflection - Light is a **transverse wave** that travels at **300,000,000 m/s** (speed of light). - Transverse waves have vibrations **perpendicular** to the direction of wave travel. ### Specular Reflection - Occurs on **smooth surfaces** like mirrors. - Rays reflect in one direction. - **Law of Reflection**: The angle of incidence equals the angle of reflection. - **Incident ray**: ray approaching the surface. - **Reflected ray**: ray leaving the surface. - **Normal**: imaginary line perpendicular to the surface at the point of incidence. - **Angle of incidence**: angle between incident ray and normal. - **Angle of reflection**: angle between reflected ray and normal. ### Diffuse Reflection - Occurs on **rough surfaces**. - Rays reflect at many angles because the surface is uneven. - The law of reflection still holds for each individual ray. ### Key Points - The law of reflection applies to all waves, not just light. - The angle of incidence is measured from the **normal**, not the mirror surface.

Transverse wave: A wave where the vibration is perpendicular to the direction of wave travel.
Speed of light: 300,000,000 m/s.
Specular reflection: Reflection from a very smooth surface where rays are reflected in one direction.
Diffuse reflection: Reflection from a rough surface where rays are reflected at many angles.
Law of reflection: The angle of incidence is equal to the angle of reflection.
Incident ray: The ray of light approaching the mirror.
Reflected ray: The ray of light leaving the mirror.
Normal: An imaginary line drawn at 90° to the mirror at the point of incidence.
Angle of incidence: The angle between the incident ray and the normal.
Angle of reflection: The angle between the reflected ray and the normal.

Flashcards

What is the speed of light?

300,000,000 m/s (the speed of light).

What type of wave is light?

Light is a transverse wave.

What causes transverse waves?

A vibration that is perpendicular to the direction of wave travel.

What is specular reflection?

Reflection from a very smooth surface like a mirror.

What is the incident ray?

The ray going into the mirror.

What is the normal?

An imaginary line drawn at 90° to the mirror.

How is the angle of incidence measured?

Between the incident ray and the normal.

How is the angle of reflection measured?

Between the reflected ray and the normal.

State the law of reflection.

The angle of incidence is equal to the angle of reflection.

Does the law of reflection apply only to light?

No, it also applies to other waves.

What is diffuse reflection?

Reflection from a surface that is not smooth, where rays are reflected at many angles.

Does the law of reflection hold for diffuse reflection?

Yes, the angle of incidence still equals the angle of reflection for each ray, but the surface points in different directions.

Why do we see ourselves in a mirror?

Because mirrors reflect light.

What is the electromagnetic spectrum?

A family of seven transverse waves that includes light.

True or false: Light is a transverse wave.

True.

True or false: Transverse waves are caused by a vibration perpendicular to wave travel.

True.

True or false: Diffuse reflections happen from a very smooth surface.

False. Specular reflections happen from smooth surfaces.

True or false: In diffuse reflection, the angle of incidence is not always equal to the angle of reflection.

False. The law of reflection still holds for each ray.

True or false: The angle of incidence is measured from the incident ray to the mirror.

False. It is measured from the incident ray to the normal.

True or false: Only light obeys the law of reflection.

False. Other waves also obey it.

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