Lesson objectives Teachers' notes

1)Students will discover how light interacts with certain types of surfaces

2) Students will understand the laws governing the phenomenon of reflection

3) Discover how images are formed, and their characteristics

Reflection of Light

What do you see?

How do you see it?

do you see what I see?

Teachers' notesLesson objectives

Subject:

Topic:

Grade(s):

Prior knowledge:

Cross-curricular link(s):

Physics

Reflection of Light

11

Waves, Ellectromagnetic Spectrum, Basic Reflection of Light, the eye

Geometry

Lesson notes:

This lesson activity focuses on students' knowledge of the 2 types of reflection, geometry of reflection, reflection on a plane mirror: laws of reflection, reflection on spherical mirrors, images.

Types of reflection

Specular reflection 

Reflection refers to the change in the direction of light after it meets a surface that returns it to its original medium.

occurs on a smooth surface such as a mirror, calm body of water, polished metal. The light rays are parrallel before and after the rays reach the surface.

Types of reflection\ 

Diffuse reflection

Reflection refers to the change in the direction of light after it meets a surface that returns it to its original medium.

occurs on a rough, matte, or dull surface such as rock, rough water, wood, brick, paper. The light rays are reflected in a disorderly manner (not parallel), the reflect in different directions. No discernable image is produced however it allows us to see objects around us, our eyes detect the light rays.

Specular reflection λ ≥ irregularities on surface

(smooth surface)

Diffuse reflection λ ≤ irregularities on surface

(bumpy surface)

What determines whether it is specular or diffuse? λ

Types of reflection

Specular reflection 

Diffuse reflection

Reflection refers to the change in the direction of light after it meets a surface that returns it to its original medium.

Geometry of reflection

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surface ( tangent)⊥Plane of incidence: defined by the incident ray and normal.Incident ray: light ray that travels toward the reflective surfaceAngle of incidence (θi): formed by the incident ray and the normal Reflected ray: light ray travels away from the reflective surfaceAngle of reflection (θr): formed by the reflected ray and the normal

Terminology

Geometry of reflection

Terminology

Incident ray: light ray that travels toward the reflective surface

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surfacePlane of incidence: defined by the incident ray and normal.Angle of incidence: formed by the indicent ray and the normalReflected ray: light ray travels away from the reflective surfaceAngle fo reflection: formed by the reflecten ray and the normal

Geometry of reflection

Terminology

Incident ray: light ray that travels toward the reflective surface

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surfacePlane of incidence: defined by the incident ray and normal.Angle of incidence: formed by the indicent ray and the normalReflected ray: light ray travels away from the reflective surfaceAngle fo reflection: formed by the reflecten ray and the normal

2 Laws of reflection

Incident ray: light ray that travels toward the reflective surface

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surfacePlane of incidence: defined by the incident ray and normal.Angle of incidence: formed by the indicent ray and the normalReflected ray: light ray travels away from the reflective surfaceAngle fo reflection: formed by the reflecten ray and the normal

First law of reflection:the incident ray, the reflected ray and the normal are all located in the same plane (on the plane of incidence)

Incident ray: light ray that travels toward the reflective surface

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surfacePlane of incidence: defined by the incident ray and normal.Angle of incidence: formed by the indicent ray and the normalReflected ray: light ray travels away from the reflective surfaceAngle fo reflection: formed by the reflecten ray and the normal

Laws of reflection

Incident ray: light ray that travels toward the reflective surface

Normal: imaginary line (usually draw a dotted line) perpendicular to the reflective surfacePlane of incidence: defined by the incident ray and normal.Angle of incidence: formed by the indicent ray and the normalReflected ray: light ray travels away from the reflective surfaceAngle fo reflection: formed by the reflecten ray and the normal

Second law of reflection: the angle of incidence is equal to the angle of reflection: θi = θr

θi θr