Making Waves E104 – E129

How Waves Move Energy A wave is a disturbance that travels through matter or space, carrying energy from one place to another without carrying matter along with it. (Think of a rock being thrown into a pond.)

Amplitude The amplitude of a wave is the distance that any point on the wave is moved from its resting position. (Where the water would be if there was no wave.)

Wavelength The wavelength can be measured between any two identical points on the waves. From one crest to another, or one trough to another. Light waves are measured in billionths of a meter, or nanometers.

Crest & Trough The crest of a wave is the top, or highest part, peak. The trough of a wave is the low point, depression, or bottom. Wave height is the difference between the two.

Wave Structure

Different Kinds of Waves Transverse wave – vibrate at right angles in the direction of the wave. (side to side) Longitudinal wave – vibrate back and forth in the same direction as the wave is moving. (back and forth)

Frequency Frequency is the number of vibrations a wave has in a given time. Frequency is usually measured in units called hertz. Frequency is measured by counting the number of crests that pass a point in a certain amount of time. One crest in one second is 1 hertz. Two crests in one second is 2 hertz.

Electromagnetic Waves In the day, light travels millions of miles, from the sun. At night, light travels a few feet from your lamp. Both types of light travel the same way. Light is made of electromagnetic waves, a combination of vibrating electric and magnetic fields The waves travel from the sun or stars through empty space before we can see them.

Speed of Waves All waves travel at the same speed through a vacuum (empty space), but they have different wavelengths and frequencies. The range of wavelengths is call the “Electromagnetic Spectrum”.

Electromagnetic Spectrum

Radiant Energy Radiant energy is the energy carried on electromagnetic waves.

Reflection Why don’t we see all colors flying through the air all the time? We only see the light waves that are bouncing off objects and then into our own eyes. Reflection – is the bouncing of light waves off of the surface.

Refraction When light enters a new medium, the change in speed causes it to bend. Refraction – is the bending of a light wave when it passes from one medium to another.

Transparent Substances that light can travel through are transparent. Air, water, clear glass, and clear plastic are transparent. You can see object clearly through them.

Opaque Substances that light can’t travel through are opaque. Opaque objects absorb or reflect light. They are wood, pottery, bricks, animals, and people.

Translucent Some objects are not completely opaque, but let some light through. But because they are not completely transparent, you can’t see clearly through them. They are milky plastics, frosted glass, and stained glass.

Absorbed Sometimes when light waves with a single frequency strike an object, the light waves could be absorbed and converted into heat.