DAILY QUESTION March 12, State the law of reflection.

Agenda3/12/09 Daily Question Turn in: Electromagnetic Sign Brain Pop – “Electromagnetic Spectrum” 15-3 Notes Brain Pop – “Color” Assignments: /3 Worksheet due 3/13

Another model for light is the light ray It is used to describe: –Reflection –Refraction A light ray is: –An imaginary line running in the direction that the light travels –It is in the same direction of wave travel or the path of the photon

The study of light in cases in which light behaves like a ray is called geometrical optics Using light rays, one can trace the path of light in geometrical drawings called ray diagrams

When a beam of light is reflected, the path: Of each light ray in the beam changes from its initial direction to another direction

If the surface is rough: –Light striking the surface will be reflected at all angles Reflection of light in random directions is called diffuse reflection

If the surface is smooth: –All the light hitting the mirror from one direction is reflected together into a single new direction

The new direction of the light rays is related to the old direction in a definite way –The law of reflection states: The angle of incidence equals the angle of reflection

Flat mirrors form virtual images by reflection. The image that you see results from: the apparent path of the light rays, not an actual path. –An image of this type is called a virtual image

Curved mirrors can distort images. Curved mirrors still create images by reflecting light according to the law of reflection. But: –Because the surface is not flat, the line perpendicular to the mirror points in different directions for different parts of the mirror

Convex Mirrors –Mirror that bulges out –Two light rays that start out parallel are reflected into different directions –Image is stretched out Concave Mirrors –Mirror that are indented –Reflect two parallel rays in toward one another –Image is compressed

A concave mirror can form two kinds of images: –Virtual image –Real image A real image results when: –Light rays from a single point of an object are focused onto a single point or small area

The primary difference between a real and a virtual image is: –With a real image, light rays really exist at the point where the image appears –A virtual image appears to exist in a certain place, but there are no light rays there

The different wavelengths of visible light correspond to many of the colors that you perceive. Objects have color because: –They reflect certain wavelengths –White light from the sun actually contains light from all the visible wavelengths of the electromagnetic spectrum

Colors may add or subtract to produce other colors. Black is: –Not really a color at all It is the absence of color