The Ray Model of LightThe Ray Model of Light

Light travels in straight lines:

Laser

Part 1 – Properties of Part 1 – Properties of LightLight

Light travels VERY FAST – around 300,000 kilometres per second.

At this speed it can go around the world 8 times in one second.

• A luminous object like a candle radiates light in all directions• We can use a light ray, which is a line and arrow showing the direction light is travelling, to show this.

• Using Light rays to show the path of light striking an object is called Geometric Optics

• When light emitted from a source (the Sun) strikes an object (Earth), it is called Incident Light

Recall:

• A transparent object lets light pass through it easily

3 Classifications of 3 Classifications of MatterMatter

Recall:

• A translucent object allows some light to pass through

3 Classifications of 3 Classifications of MatterMatter

Recall:

• An opaque material does not let any light pass through it

3 Classifications of 3 Classifications of MatterMatter

• An image is a reproduction of an original object that is produced through the use of light

• A mirror is any polished surface that exhibits reflection• Reflection is simply the

bouncing back of lightfrom any surface

Part 2 - ReflectionPart 2 - ReflectionReflection from a mirror:

Incident ray

Normal

Reflected ray

Angle of incidence

Angle of reflection

Mirror

ActivityActivity

• In your lab groups, try Activity 11.5 on Page 482 and 483

The Law of ReflectionThe Law of Reflection

Angle of incidence = Angle of Angle of incidence = Angle of reflectionreflection

In other words, light gets reflected from a surface at ____ _____ angle it hits it.

The same !

!!

Clear vs. Diffuse ReflectionClear vs. Diffuse Reflection

Smooth, shiny surfaces have a clear reflection:

Rough, dull surfaces have a diffuse reflection.

Diffuse reflection is when light is scattered in different directions

Specular ReflectionSpecular Reflection

• Specular reflection is the reflection of light off a smooth surface

The water acts like a plane mirror Disco rules!

Using mirrorsUsing mirrorsTwo examples:

1) A periscope

2) A car headlight