Light exists in PHOTONS which have the properties of a WAVE and a PARTICLE.
Light rays refract when they go from one medium to another. The angle of refraction depends on the angle of incidence (the angle in which the light ray enters) and the index of refraction for the medium. Click here to explore a Refraction of Light Applet
To find the angle of refraction, use the equation...
...where v is velocity in m/s and n is index of refraction
The SPEED of LIGHT is 3.0x10^8 m/s
There are three basic types of mirrors: Plane, Convex, and Concave.
Plane Mirror
Convex Mirror
Concave Mirror
Each mirror reflects a different variation of the original image.
To find out exactly what is going on when the image is reflected in each mirror, we can ask these three questions:
1. Is the image upright or inverted?
2. Is the image real or virtual?
3. Is the image enlarged, diminished, or the same size?
Real Image - The light rays diverge, or meet where the image is formed.
Virtual Image - The light rays appear to diverge, but do not actually meet, but form an image.
Focal Point - Where the light rays in a mirror or lens converge
Focal Length - The distance from a lens or a mirror to its focal point.
Real images are always inverted, or upside down.
Virtual images are always upright, or right side up.
Characteristics of each mirror:
Plane Mirror
The image is always upright.
The image is always virtual.
The image is always the same size.
This applet shows the reflections on a plane mirror.
The Plane Mirror Game is an interactive way to see light reflection from a plane mirror.
Convex Mirror
The image is always upright.
The image is always virtual.
The image is always diminished.
This applet shows the reflections of a convex mirror.
Concave Mirror
Concave Mirrors behave differently, depending on the location of the object being reflected.
When the object is located inside the focal point (F), the image is virtual, enlarged, and upright.
When the object is located at the focal point, the light rays reflect parallel to each other, never forming an image.
When the object is located between the focal point (F), and the center of curvature (2F), the image is real, inverted, and enlarged.
When the object is located at the center of curvature (2F), the image is real, inverted, and the same size.
When the object is located beyond the center of curvature (2F), the image is real, inverted, and diminished.
This applet shows the many types of reflections on a concave mirror.
When looking at lenses and mirrors, remember to use this equation:
p=object distance
q=image distance
f=focal length
To find magnification, use this equation:
m=-q/p
Concave Lenses
Double-Concave, or diverging lenses, form virtual, upright images, because these lenses have a virtual focal point.
This means that focal length is negative!
Convex Lenses
Double-Convex, or converging lenses, have a real focal point, and therefore form real,inverted images.
Focal length for these lenses is positive.
Light rays converge differently and form different image sizes depending on the relation between object location and the location of the focal length.
Click here to see the different cases of ray diagrams for converging lenses:
