Waves

Waves A wave can be described as a disturbance that travels through a medium from one location to another location. There are three types of waves: 1. Mechanical waves require a material medium to travel (air, water, ropes). These waves are divided into three different types. o Transverse waves cause the medium to move perpendicular to the direction of the wave. o Longitudinal waves cause the medium to move parallel to the direction of the wave. o Surface waves are both transverse waves and longitudinal waves mixed in one medium. 2. Electromagnetic waves do not require a medium to travel (light, radio). 3. Matter waves are produced by electrons and particles. The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium. Suppose that a hand holding the first coil of a slinky is moved back and-forth two complete cycles in one second. The rate of the hand's motion would be 2 cycles/second. The first coil, being attached to the hand, in turn would vibrate at a rate of 2 cycles/second. The second coil, being attached to the first coil, would vibrate at a rate of 2 cycles/second. In fact, every coil of the slinky would vibrate at this rate of 2 cycles/second. This rate of 2 cycles/second is referred to as the frequency of the wave. The electromagnetic spectrum is a range of all electromagnetic waves arranged according to frequency and wavelength. Radio waves are used to transmit radio and television signals. Radio waves have wavelengths that range from less than a centimeter to tens or even hundreds of meters. Microwave wavelengths range from approximately one millimeter to thirty centimeters. In a microwave oven, the radio waves generated are tuned to frequencies that can be absorbed by the food. Infrared is the region of the electromagnetic spectrum that extends from the visible region to about one millimeter (in wavelength). Infrared waves include thermal radiation.

The rainbow of colors we know as visible light is the portion of the electromagnetic spectrum with wavelengths between 400 and 700 billionths of a meter. Ultraviolet radiation has a range of wavelengths from 400 billionths of a meter to about 10 billionths of a meter. Sunlight contains ultraviolet waves which can burn your skin. X-rays are high energy waves which have great penetrating power and are used extensively in medical applications and in inspecting welds. Gamma rays have wavelengths of less than about ten trillionths of a meter. They are more penetrating than X-rays. Gamma rays are generated by radioactive atoms and in nuclear explosions. Materials like air, water, and clear glass are called transparent. When light encounters transparent materials, almost all of it passes directly through them. Materials like frosted glass and some plastics are called translucent. When light strikes translucent materials, only some of the light passes through them. The light does not pass directly through the materials. It changes direction many times and is scattered as it passes through. Most materials are opaque. When light strikes an opaque object none of it passes through. Most of the light is either reflected by the object or absorbed and converted to heat. Refraction is the bending of the path of a light wave as it passes across the boundary separating two media. Refraction is caused by the change in speed experienced by a wave when it changes medium. Regardless of the angle at which the wave fronts approach the barrier, one general law of reflection holds true: the waves will always reflect in such a way that the angle at which they approach the barrier equals the angle at which they reflect off the barrier. This is known as the law of reflection.