refraction and lenses

Refraction and LensesChapter 4 – Section 3

Refraction

• The speed of light– The speed of light in

empty space is about 300,000,000 m/s

– Light travels more slowly when it travels through material such as air, water, or glass.

What would happen?

Refraction

• The bending of light waves caused by a change in speed as they pass through different media is called refraction.

Lens

• Lens – transparent object with at least one curved side that causes light to bend

• Two types of lenses – convex lens and concave lens

Convex Lens

• A convex lens is thicker in the center than at the edges.

• The light waves converge when they pass through the lens.

Convex Lens

• If the object is more than two focal lengths from the lens, the image formed is smaller than the object and inverted.

Convex Lens

• If the object is closer to the lens than one focal length, the image formed is enlarged and upright.

Concave Lens

• A concave lens is thicker at the edges than at the middle.

• It causes light rays to diverge forming an upright image smaller than the actual object.

Concave Lens

• The image will be smaller and upright if the object is more than two focal lengths from the lens and also when it is closer than one focal length from the lens.

Total Internal Reflection

• Total internal reflection occurs when all the light waves that strike the boundary between two transparent materials can be reflected, meaning that you can see your reflection in a transparent material like water or glass.

• At the critical angle all light is reflected.

• The size of the critical angle depends on the two materials involved.

Total Internal Reflection