RAY MODEL OF LIGHT The Ray Model of

RAY MODEL OF LIGHT

The Ray Model of Light • Some properties of light are best described by considering light as a wave. • Other properties of light are best described by considering light as a particle. • The ray model of light uses a straight line, or ray, to show the direction the light wave is travelling.

Ray Model of Light • The Ray Model of Light is good for: –Studying optics –Studying how light reflects off mirrors –Studying how light passes through lenses

Light and Matter • Different materials can either transmit, absorb, or reflect light. Transparent • Objects allow light to pass through freely. • Objects transmit light (allows light through without being completely absorbed) • Ex. Drinking glass, clear window See pages 169 - 170

Transparent

Translucent • Objects allow scattered light through • Light changes in different directions after passing through object • Object is not seen clearly • Ex. Washroom glass bricks or windows

Translucent

Opaque • Objects prevent all light from passing through. • All light is absorbed or reflected • Ex. Black curtains, ceramic mug

Opaque

Shadows • A shadow is created when an opaque object absorbs light rays from alight source that is in front of the object • The Ray Model of Light can be used to predict the position, size and sharpness of a shadow See page 171

How does light form shadows? light source ☼Light rays travel in straight lines, radiating out from the light source. ☼If rays are blocked by an opaque object a shadow forms where the light cannot reach. ☼If the light source is moved closer to the object, more light is blocked and a larger shadow is formed.

Light Can be Reflected • Reflection is when light bounces off an object. – To act like a mirror, the surface must be smooth. • The incoming ray of light is called the incident ray. Incident ray Reflected ray • The ray that bounces off the surface is called the reflected ray.

THE LAW OF • The normal is an imaginary line perpendicular REFLECTION to the surface. • The angle of incidence (i) is measured from the normal to the incident ray. • The angle of reflection (r) is measured from the normal to the reflected ray. The angle of incidence equals the angle of reflection.

Light Can be Refracted • When light travels from one transparent medium to another transparent medium it changes speed. – This change in speed causes the light to change direction. • The bending of light, due to a change in speed, is called refraction. • The angle of refraction is measured from the refracted ray to the normal.

Refraction of Light in Water and Air • Objects in water appear in a different location than they actually are. This is due to the refraction of the light. • Light refracts when it passes through air at different temperatures. – For example, a mirage is the light from the sky bending as it approaches the warm air near the ground.

Mirage on the road looks with a pool of water, but are actually images of the sky refracted by warm air near the ground