Electromagnetic Waves
They are waves which can travel through a vacuum.
Creation of Electromagnetic Waves
When a charged particle creates an oscillating electric field, an oscillating magnetic field is generated by the attracted positive particle. This all begins at the source of the wave. The vibrations in the fields then create a wave in which the two fields are perpendicular to each other. Because of this, electromagnetic waves move in a similar way to transverse mechanical waves.
Electric Field
The electric field surrounding the one with the negative charge (blue) draws in the positive charge.
Electromagnetic Wave
The wave moves away from the source with the electric and magnetic waves perpendicular to each other.
Transverse Wave
Rather than having two fields perpendicular to each other like electromagnetic waves, particles of the medium move perpendicular to the mechanical transverse wave.
Electromagnetic vs. Mechanical Waves
There are many ways that electromagnetic and mechanical waves contrast, such as:
- Mechanical waves require a medium; electromagnetic ones can travel through a vacuum.
- Rather than being categorized by the way they change the position of the particles within the medium like mechanical waves, electromagnetic waves are sorted by how high or low their wavelengths and frequencies are.
The Electromagnetic Spectrum
Electromagnetic radiation, the type of energy released by waves, can have many different frequencies, energy levels, and wavelengths. The electromagnetic spectrum is the range of these characteristics which organizes different types of electromagnetic radiation. Along the illustration above, the names of each type of radiation are listed periodically. Waves with a longer wavelength are on the left, and waves with a shorter wavelength are on the right; this means that the waves of a higher frequency and energy level are on the right, and waves of a lower frequency and energy level are on the left. Below are both the types of radiation on the spectrum and the energy which is transported by electromagnetic waves.
Types of Electromagnetic Radiation
Radio
Radio waves have the longest wavelength of greater than 1 x 10^-1 m, meaning that they also have the lowest frequency (less than 3 x 10^9) and level of energy (less than 2 x 10^-24). They are commonly used on television, radios, and by police officers to detect speed.
Microwave
Microwaves have a very low frequency (from 3 x 10^9 to 3 x 10^11 Hz) and energy (2 x 10^-24 to 2 x 10^-22 J). They also have very long wavelengths (1 x 10^-3 to 1 x 10^-1 m). They are used in cooking and in cell phones.
Infrared
Infrared waves have both low frequency (3 x 10^11 to 4 x 10^14 Hz) and energy levels (2 x 10^-22 to 3 x 10^-19 J)but also have long wavelengths (7 x 10^-7 to 1 x 10^-3 m). We use them every day in television remote controls and toasters.
Visible Light
Visible light is what we use to see; objects such as light bulbs and lamps also emit it. Its wavelength is from from 4 x 10^-7 to 7 x 10^- m. Its frequency is from 4 x 10^14 to 7.5 x 10 ^14 Hz, and its energy is from 3 x 10^-19 to 5 x 10-19 J. This all makes visible light the middle of the spectrum.
Ultraviolet
Ultraviolet radiation has a high frequency (7.5 x 10^14 to 3 x 10^16 Hz), low wavelength (1 x 10^-8 to 4 x 10^-7 m), and high energy level (5 x 10 ^-19 to 2 x 10^-17 J). The sun releases the most of this type of radiation (although there is some visible light and infrared radiation). Although it can cause cancer in some cases, this is also used in sun beds, security pens, and fluorescent lights. It is also used to to detect counterfeit money.
The picture above shows the sun.
X-ray
In almost all hospitals, x-rays are used to look at images of bones and check for cracks in metal. These are both possible to do because of this wave’s very high frequency (3 x 10^16 to 3 x 10^19 Hz), very short wavelength (1 x 10^-11 to 1 x 10^-8 m), and very high level of energy (2 x 10^-17 to 2 x 10^-14 J).
The picture above shows an x-ray of a chest.
Gamma Rays
Gamma rays have the highest level of energy (more than 2 x 10^-14 J) and frequency (more than 3 x 10^19 Hz) on the spectrum. Because of this, its wave length is also the shortest in comparison to the other types of radiation (less than 1 x 10^-11 m). They are frequently used for killing cancer cells and sterilizing surgical instruments.
The picture above shows the device used to destroy cancer cells.
Electromagnetic waves and the electromagnetic spectrum | Physics | Khan Academy
Watch this video to learn more about electromagnetic waves and the electromagnetic spectrum!
This presentation was created by Isabelle deBruler.