1. electromagnetic spectrum          10. reflection
                                             2. light                                          11. refraction
                                             3. transverse wave                        12. lens
                                             4. wavelength                                13. concave lens
                                             5. frequency                                  14. convex lens
                                             6. hertz                                         15. mirror
                                             7. radiation                                    16. real image
                                             8. photon                                       17. virtual image
                                             9. optics                                        18. opaque
 
 

LIGHT: a form of energy that travels in waves.

WAVE - is a rhythmic disturbance that carries energy; it transfers energy from one place to another.

TYPES OF WAVES:
1. light
2. radio
3. x-rays
These types of waves are very different, yet have things in common. Radio, light, and x-rays all use electromagnetic waves.

ELECTROMAGNETIC WAVES: are transverse that carry energy through "empty space" at a velocity of 3,000,000 kilometers per second (186,000 miles/second)

NOTE: The transfer of energy by electromagnetic waves is called RADIATION. Example: sunlight

TRANSVERSE WAVES: A wave where matter vibrates at right angles to the direction in which the wave travels.

transverse wavelength crest
wave

trough

Light as seen by the eyes is a part of the ELECTROMAGNETIC SPECTRUM.

ELECTROMAGNETIC SPECTRUM - a listing of different electromagnetic waves arranged in order of their wavelength and frequency.

NOTE: Electromagnetic waves are produced electricity or magnetism.

WAVELENGTH - the distance between the point on one wave and the same identical point on the next wave.
wavelength

FREQUENCY - a count of the number of waves that pass a given point in one second.
F=waves/seconds

NOTE: Frequency is measured in a unit called a hertz (Hz). One hertz (Hz) is one wave per second. Example: In sound waves, the frequency of the note "middle c" is 262 Hz, this means the sound vibrates 262 times per second.
 

NOTE: Although wavelength differ in length and frequency, they travel through space at the same velocity.

VISIBLE LIGHT - a form of energy that travels in waves. Visible light is one part of the electromagnetic spectrum. Like the other waves of the electromagnetic spectrum, light is made of PHOTONS.

PHOTON - a tiny packet of radiant energy.

Each color of light has a different wavelength and frequency. Frequency (waves/sec.) of a light wave determines its color.

EXAMPLES: the wavelength of a violet light is 0.00004cm
the wavelength of red light is 0.00007cm

OPTICS - is the science that is devoted to the study of light and its uses.

WHITE LIGHT - is formed when all colors of light are mixed together.
- When white light is passed through a prism, the colors separate into a color spectrum (colors of a rainbow).
 
 
 
 
 
 
 
 
 
 
 
 
 

The colors are created through reflection and refraction of the light as it hits the prism.

REFLECTION - bouncing of a wave off a surface; change in directions.
 
 
 
 
 

REFRACTION - the bending of a wave, caused by a decrease in speed as it passes from one material to another.
Example: This change of speed is what creates a visual distortion such as that of an object that has been dropped into a glass container of clear liquid.
 
 
 
 

DIFFRACTION - a method of separating light into the spectrum of colors (using slits in glass or plastic).

NOTE: According to the law of reflection, the angle at which light reflected from a surface is the same as the angle at which it strikes the surface, this creates a reflection such as that produced with a mirror.

ABSORBING LIGHT:

TRANSPARENT - objects that allow light to pass through (transmits light).
OPAQUE - objects that absorb all the light.
TRANSLUCENT - objects that transmit some light, but do not allow you to see clearly through them.

LENS - a curved transparent object; usually made of glass or clear plastic.
Examples: lenses are used in telescopes, eyeglasses, microscopes, projectors, cameras, watches.

NOTE: a lens will refract light differently depending whether it is convex or concave.

CONVEX LENS - a lens that bends light waves to bring them together to a central focus point in front of the lens. Convex lenses are thicker in the middle than at the edges.
 
 
 
 
 
 
 
 
 
 

Example: a magnifying glass, convex lenses are also used in eyeglasses to correct farsightedness.

CONCAVE LENS - a lens that bends the light waves away from the central point of the lens, forming a fan shape of light waves in front of the lens. Concave lenses are the thinner in the middle and thicker at the edges.

Example: concave lenses are used in eyeglasses to correct nearsightedness.

NOTE: Lenses and mirrors can produce different kinds of images (real images or virtual images).

MIRROR - a device that reflects light to form an image (mirrors can be flat or curved).
- a plane mirror in flat
- a parabolic mirror is curved
two types of parabolic mirrors
a. concave mirror - curved like the inside of a bowl of a spoon.
b. convex mirror - curved like the back of a spoon

VIRTUAL IMAGE - an image formed by a mirror or lens that can not be projected onto a surface and from which light only appears to come.

Example: When looking at your image in a plane mirror, your image seems to be behind the mirror, it appears to be the same distance behind the mirror as you are in front of it. In reality there is nothing behind the mirror, the image only appears to be there.

REAL IMAGE - an image that can be projected onto a screen, it is formed by a curved (parabolic) mirror or convex lens. The light rays actually meet at a point in space, if you put a piece of paper there, you could see the image on it.

Example: an image produced by a movie projector light, and x-rays all use electromagnetic waves.

ELECTROMAGNETIC WAVES: are transverse that carry energy through a vacuum or matter.