Waves
What are waves? A wave is disturbance that moves through matter and space and carries energy. They're all around you. There are waves in the air that your TV gives off, your computer screen gives off, the radio waves in the air. So we are going to teach you a couple things you ought to know. First, a very important fact, waves carry energy, not matter. There are four types of waves. Transverse, compressional, electromagnetic, and mechanical, each of which have their differences.
Transverse first. Transverse waves are mechanical waves that can have, but do not need, a medium. It causes particles in matter to move move back and forth at right angles to the direction it travels. These waves have high and low points, called crests and troughs. This series of crests and troughs makes the transverse wave you see in the image below.
Transverse first. Transverse waves are mechanical waves that can have, but do not need, a medium. It causes particles in matter to move move back and forth at right angles to the direction it travels. These waves have high and low points, called crests and troughs. This series of crests and troughs makes the transverse wave you see in the image below.
A second type of mechanical wave is called a compressional wave. This type of wave causes particles in matter to move back and forth along the same direction the wave travels. You can think of a compressional wave as a slinky going back and forth. The areas that are squeezed together are called compressions. The places where the particles are spread apart are called rarefactions. The pattern of compressions and rarefactions form a compressional wave. The compressions and rarefactions travel across the spring, but the coils move only back and forth.
Lastly, we have the electromagnetic waves. X-rays, radio waves, and light are all examples of electromagnetic waves. Electromagnetic waves are transverse waves, but they have electric and magnetic parts that vibrate up and down perpendicular to the direction the wave travels.
Properties
Waves aren't just waves. They have many properties that define them. The first of these properties is wavelength. A simple definition: The distance between one point on a wave and the nearest point moving with the same speed and direction.. Usually the wavelength is the measure taken between two side-by-side crests or two side-by-side troughs on a transverse wave. The same goes for compressional wave, except the points are compressions or rarefactions.
The second property is frequency. Frequency is the number of wavelengths that pass a given point in a second. It is measured in hertz (Hz). A higher frequency wave has shorter wavelengths, while a lower frequency wave has a longer wavelength. With sound waves, higher frequency waves mean higher pitched sounds, and vice versa.
The third is amplitude. In a transverse wave, the amplitude is half the distance between the crest and trough. In a compressional wave, the amplitude depends on the density of the material and the length of compressions and rarefactions. A wave with a higher amplitude has more compressed compressions and more spread out rarefactions. In sound waves a higher amplitude means a louder sound.
The second property is frequency. Frequency is the number of wavelengths that pass a given point in a second. It is measured in hertz (Hz). A higher frequency wave has shorter wavelengths, while a lower frequency wave has a longer wavelength. With sound waves, higher frequency waves mean higher pitched sounds, and vice versa.
The third is amplitude. In a transverse wave, the amplitude is half the distance between the crest and trough. In a compressional wave, the amplitude depends on the density of the material and the length of compressions and rarefactions. A wave with a higher amplitude has more compressed compressions and more spread out rarefactions. In sound waves a higher amplitude means a louder sound.
Changing Direction
Many people think that waves just travel in one direction. But waves can also reflect, refract, and diffract when they hit different materials. I will talk about each in turn.
I will first explain reflection. You see this everyday in your bathroom mirror. This is because light is reflecting off the mirror and hitting your eye. When light reflects off an object, it always follows the law of reflection, which states that the angle at which the wave hits will equal the angle at which it reflects.
Next, I will explain refraction. Refraction is the change in direction of a wave when it changes speed as it travels from one material to another . For example, light waves change speed when passing from air into water. This can distort objects that are in both materials.
Waves can also change direction by means of diffraction. diffraction is the bending of waves around an object . The amount of diffraction depends on the size of the object that it is trying to move around. If the object is larger than the wavelength, very little diffraction occurs. As the wavelength increases to the size of the obstacle or larger, the amount of diffraction increases.
I will first explain reflection. You see this everyday in your bathroom mirror. This is because light is reflecting off the mirror and hitting your eye. When light reflects off an object, it always follows the law of reflection, which states that the angle at which the wave hits will equal the angle at which it reflects.
Next, I will explain refraction. Refraction is the change in direction of a wave when it changes speed as it travels from one material to another . For example, light waves change speed when passing from air into water. This can distort objects that are in both materials.
Waves can also change direction by means of diffraction. diffraction is the bending of waves around an object . The amount of diffraction depends on the size of the object that it is trying to move around. If the object is larger than the wavelength, very little diffraction occurs. As the wavelength increases to the size of the obstacle or larger, the amount of diffraction increases.
reflection of light waves refraction of light passing from air into water
Sound Waves
One type of compressional wave is a sound wave. Sound waves need a medium to travel, meaning that they can only travel through matter. These waves are produced by vibrations. For example, when a musician plays a guitar, the strings vibrate, creating the sounds that you hear. Air particles that are nearby vibrate with the same frequency as the vibrations. The vibrations moving inward and outward create the compressions and refractions, and those vibrations hit more and more particles, until they reach you. The energy that sound waves carry is transferred by the collision, or connection, between the particles in the material that the wave is currently traveling in. This is why we have the strange saying "No one can hear you scream in space." It is literally true, as in space there are no particles for sound waves to travel through.
Speed of Sound
The speed of sound can be changed by two things: The density of the medium and the temperature of the medium. The denser a medium, the faster the wave travels, because there is so much more matter to travel through. Similarly, sound waves travel faster through materials that have a higher temperature.
Loudness of Sound
The loudness of sound depends on the energy put into it. There are some different characteristics in the loudness of sound. The first I will talk about is intensity. Intensity is the amount of energy a wave carries past a certain point in a second. Sound with a greater amplitude also has a greater intensity. The intensity of sound waves is measured in decibels (dB).
Pitch and Frequency
Pitch is the human perception of sound. The pitch we hear is dependent on the frequency of the wave. A higher frequency means a higher pitched wave.