7.6.c Students know light travels in straight lines if the medium it travels through does not change.

7.6.g Students know the angle of reflection of a light beam is equal to the angel of incidence

When an object or wave hits a surface through which it cannot pass, it bounces back.

Angle of incidence- Angle between the incoming wave and the normal

Angle of reflection- angle between the reflected wave and the normal

Key concept: The law of reflection states that the angle of incidence equals the angle of reflection.

Light travels in straight lines unless the medium it is traveling through changes

When light hits a shiny surface it bounces back

Image- copy of an object formed by reflected or refracted rays of light

Optical axis- an imaginary line that divides a mirror in half

Focal point- point where rays parallel to the optical axis meet or converge

Mirrors: Plane Mirrors•Plane mirror- flat sheet of glass that has a smooth, silver-colored coating on the one side

•Image appears to be as far behind the mirror as the object is in front of the mirror

•The reflected light from an object looks as through it came from a point behind the mirror

•Creates a virtual image that is upright and same size- but not quite the same

•Virtual image- upright image that forms where light seems to come from (image appears behind mirror)

•Real image- forms when rays actually meet

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A mirror with a surface that curves inward like the inside of a bowl is a concave mirror.

Reflects rays that are parallel back through the focal point

Mirrors: Concave Mirrors

Concave mirrors can form either virtual images or real images.

The location of the focal point depends on the shape of the mirrors

Concave mirrors can either be can be either virtual or real

Virtual images formed by a concave mirror are always larger than the image

Object in mirror are closer than they appear

Can never create a real image because the rays never meet

Disadvantage: image is reduced in size- appears to be further away than it is

Advantage: allows you to see a larger area than you can with a plane mirror

Where they are used: security, passenger side mirrors, safety mirrors in banks, parking garages, offices

A mirror with a surface that curves outward is called a convex mirror.

Key Concept: When light rays enter a medium at an angle, the change in speed causes the rays to bend, or change direction.

Light travels in straight lines if the medium does not change

If light enters a new medium it might slow down or speed up

•Different densities in the same medium cause refraction

•Stars twinkle because of variations in the density in the Earth’s atmosphere

•Rainbows are a pretty effect caused by refraction- it is the separation of the visible light

•The longer the wavelength the less the wave is bent by a prism

Lens- a curved piece of glass or other transparent material that refracts light

A lens forms an image by refracting light rays passing through it

The type of image formed depends on the shape of the lens and the position of the object

Focal length- the distance from the lens to the focal point

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Key Concept: An object’s position relative to the focal point determines whether a convex lens forms a real image or a virtual image.

Convex lens- thicker in the center than the edge

Key concept: A concave lens can produce only virtual images because parallel light rays passing through the lens never meet.

Concave lens- thinner in the center than the edges