REFLECTION OF LIGHT

Light

Part 1 – Properties of Light

• Light travels in straight lines:

Laser

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

At this speed it can go around the world 7.5 times in one second.

• Light travels much faster than sound. For example:

1) Thunder and lightning start at the same time, but we will see the lightning first.

2) When a starting pistol is fired we see the smoke first and then hear the bang.

• Luminous and non-luminous objects

A luminous object is one that produces light.

A non-luminous object is one that reflects light.

Luminous objects Nonluminous objects

• Shadows

Shadows are places where light is “blocked”:

Rays of light

Properties of Light summary

1) Light travels in straight lines2) Light travels much faster than sound3) We see things because they reflect light into

our eyes4) Shadows are formed when light is blocked by

an object

How do we see objects?

• We see things because they reflect light into our eyes:

Homework

Reflection

Reflection of Light

•is the phenomenon of wave motion, in which a wave is returned after impinging on a surface.

Types of Reflection

Specular Reflection•Reflection off of smooth surfaces such as mirrors or a calm body of water.

Diffuse Reflection•Reflection off of rough surfaces such as clothing, paper, and the asphalt roadway.

Applications

One application pertains to the relative difficulty of night driving on a dry asphalt roadway compared to a wet asphalt roadway.

The Law of Reflection

The incident ray, the reflected ray, and the normal to the surface all lie in the same plane, and the angle of reflection θr equals the angle of incidence θi.

The ray of light approaching the mirror is known as the incident ray (labeled I in the diagram). The ray of light which leaves the mirror is known as the reflected ray (labeled R in the diagram).

At the point of incidence where the ray strikes the mirror, a line can be drawn perpendicular to the surface of the mirror; this line is known as a normal line (labeled N in the diagram).

The angle between the incident ray and the normal is known as the angle of incidence.

The angle between the reflected ray and the normal is known as the angle of reflection.

Reflection• Reflection from a mirror:

Incident ray

Normal

Reflected ray

Angle of incidence

Angle of reflection

Mirror

• 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 !

!!