Grade 9 and 10 Science Mr.MacMillan

Types of Light Emissions

1. Light from the Sun

2. Light from Incandescence

3. Light from Electric Discharge

Uses of Fluorescence:Forensics

Money

Identify abnormal tissue

Theatre Performances

Types of Luminescence

• Luminescence– The emission of light by a material or

an object that has not been heated; for example fluorescence

Phosphorescence

• Light emitted due to exposure to UV light (glow in the dark products)

Chemiluminescence

• Light produce by a chemical reaction without a temperature rise

Bioluminescence

• Light produced by a biochemical reaction

Properties of Light:Laws of Reflection

• Incident Ray– A ray of light travelling from a light

source toward a surface• Reflected ray– A ray that begins at the point where the

incident ray and the normal meet• Normal – A line that is perpendicular to a surface

where a ray of light meets the surface

Ray Diagrams

Drawing Ray Diagrams

1. Plane Mirror- a flat mirror that reflects light rays in the same way that they approach the mirror.

2. Concave Mirror- a converging mirror where light rays that strike the mirror surface are reflected so they converge or “come together”, at a point.

Types of Mirrors

3. Convex Mirrors- a diverging mirror where light rays that strike the mirror surface are reflected so that they diverge, or “go apart” and they never come to a point.

• Characteristics of a plane mirror image:

1. Object size= Image Size2. Object distance from mirror= image

distance from mirror3. Attitude (orientation) is ALWAYS upright4. ALWAYS forms a virtual image5. Image is reversed- left to right

PLANE MIRRORS

• The image in a plane mirror appears to be backwards compared to how we view the object directly.

• This is why the word on the front of an AMBULANCE is written backwards- so it can be read when seen in a rear-view mirror.

• 1. A ray that strikes perpendicular to the mirror surface, reflects perpendicular to the mirror. The reflected ray is extended beyond the mirror.

• 2. A ray that strikes the mirror at any angle reflects so the angle of incidence equals the angle of reflection. The reflected ray is extended beyond the mirror.

Steps for drawing Plane Steps for drawing Plane Mirror Ray Diagrams:Mirror Ray Diagrams:

Perpendicular ray

Incident ray

Reflectedray

Ray Diagram Using 2 Points: