Unit 3 Lesson 1- Mechanical Waves
All waves can be classified into two groups: mechanical waves and electromagnetic waves
Mechanical Waves: Mechanical waves carry energy through a medium which is a solid, liquid, or a gas, e.g: sound waves carrying energy through the air. Mechanical waves are divided into two groups based on the direction in which the particles vibrate relative to the direction of the energy. They can be grouped into either transverse waves or longitudinal waves.
Transverse: These transverse waves vibrate the particles of the medium perpendicular to the direction of the wave. The highest points on a transverse wave are called crests, while the lowest points are called troughs. The distance from one crest to the next crest is referred to as the wavelength. The amplitude of a transverse wave is the distance from a crest, or trough, to the resting position of the wave. The frequency of a transverse wave can also be determined by the number of waves that pass a given point in one second. High frequency waves have crests that are closer together than low frequency waves. The frequency is measured in units called hertz
Longitudinal: Longitudinal waves vibrate the particles of the medium in the same direction of the wave. Areas where the particles are closer together are called compressions, and rarefactions are the areas where the particles are farthest apart. The wavelength of a longitudinal wave is measured from one location on a compression to the same location on the next compression. The amplitude is measured by the degree at which the particles are squeezed together at a compression or spread out at the rarefaction. Sound waves are examples of longitudinal waves. Sound waves, like all waves, travel at different speeds through solids, water, and air. The speed of the wave is determined by how far the wave travels in a given time frame
Electromagnetic Waves:
Electromagnetic waves, such as light and radio waves, can travel through matter but can also travel through the vacuum of space. They are caused by changing electric and magnetic fields. When electromagnetic waves travel through matter, they move like transverse waves.
Many types of electromagnetic waves make up the electromagnetic spectrum. The electromagnetic spectrum includes radio waves, microwaves, infrared radiation, visible light, ultraviolet light, X-rays, and gamma rays. Radio waves have the longest wavelength and smallest frequency, while gamma rays have the shortest wavelengths and highest frequencies.
Electromagnetic waves are used in everyday life. X-rays and gamma rays are used for medical purposes. Radio waves are used for communication, and microwaves are used to cook food. Infrared radiation can also be used to heat objects, while the ultraviolet light from the sun allows life to exist on Earth. In the middle of the spectrum is the visible light you can detect with your eyes.
Both electromagnetic and mechanical waves can move energy from one place to another. The various forms and properties of waves are important to the movement of this energy around the world.
Unit 3 Lesson 2- Properties of Mechanical Waves
Transverse Waves:
For transverse waves, the particles of the medium vibrate perpendicular to the direction of the wave. As the energy of the wave passes through the medium, particles move slowly up and down from their original position. The particles move farther away from their original position when there is more energy. Higher wave height means higher amplitudes and greater energy. Lower wave height indicates less energy moving through the wave.
The wavelength of a transverse wave is the distance from one crest, the highest point of the wave, to the next crest. The greater the distance between each crest, the longer the wavelength. As the wavelength increases, there are fewer wave cycles over time, and, therefore, the frequency of the wave decreases. As the wavelength decreases, the frequency of the wave increases.
Longitudinal Waves:
For longitudinal waves, the particles of the medium vibrate parallel to the direction of the wave. As the energy of the wave passes through the medium, the particles compress and then separate as the energy moves through the wave. Less displacement of the particles from the original position means less energy through the wave. This means a lower amplitude wave. More energy causes more displacement of the particles from their original position.
The wavelength of a longitudinal wave is the distance from one point on the compression (where the particles are the closest) to the same point on the next compression. The greater the distance between each compression, the longer the wavelength. As the wavelength increases, there are fewer compressions over time, and, therefore, the frequency of the wave decreases. As the wavelength decreases, the frequency of the wave increases (more compressions over time).
Speed of a wave is Speed= Wavelength x Frequency
Periodic Motion- Any motion that repeats at regular time intervals
Period- The time required for a cycle
