Science 8 Chapter 11

11.2: Reflecting Light off Surfaces

Specular Reflection

• The reflection of light off a smooth, shiny surface

Laws of Reflection

• The incident ray, the reflected ray, and the normal all lie in the same plane.

• The angle of incidence equals the angle of reflection.

Diffuse Reflection

• Occurs when light hits an irregular surface

11.3

Describing images

Optical Device

• Produces an image OF an object

There are two types of images created from an optical device

• Virtual and • Real images

Virtual image:• an image in which the outgoing rays from a point on the

object always diverge (spread apart). • It will appear to converge in or behind the optical device

(i.e., a mirror). • A simple example is a flat/plane mirror where the image

of oneself is perceived at twice the distance from oneself to the mirror.

• That is, if one is half a meter in front of the mirror, one's image will appear to be at a distance of 1 meter away (or half a meter inside or behind the mirror).

• Because the rays never really converge, one cannot project a virtual image onto a screen.

Real Image:• a representation of an object (source) in which the perceived

location is actually a point of convergence (come together at a point) of the rays of light that make up the image.

• If a screen is placed in the plane of a real image the image will generally become visible on the opaque screen.

• Examples of real images include:– the image seen on a cinema screen (the source being the

projector), – the image produced on a detector in the rear of a camera, – and the image produced on an eyeball retina (the camera and

eye focus light through an internal convex lens).

• A real image occurs where rays converge, whereas a virtual image occurs where rays only appear to converge.

• http://www.youtube.com/watch?v=zNqXtzTcIqE

Characteristics of images

1. Size (ex) image is smaller than original object)2. Attitude (upright or inverted)3. Location of image (ex.) behind the mirror4. Type (virtual or real)