Electromagnetic Waves

Elena Marshel

What's the Difference?

Electromagnetic waves are not the only kind of waves. You may have heard of a different type, called mechanical waves. There are several similarities between the two, but they're very different things. For example, while mechanical waves need a medium to travel on, electromagnetic waves need no medium and can travel through vacuums where there is no matter. Electromagnetic and mechanical waves come in different forms, too: mechanical waves come in the shape of longitudinal, transverse, and surface waves, while electromagnetic waves are found as radio, micro, infrared, visible light, ultraviolet, x-ray, and gamma ray waves.

How are they Formed?

While mechanical waves are caused by a displacement of matter, electromagnetic waves are caused by disturbances in the electric and magnetic fields. The two fields are linked together, so a change in one will cause a change in the other. Electric currents will be affected by the magnetic properties of certain materials, which cause electromagnetic waves (hence the name).
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The Spectrum

As seen above, there is a spectrum of wavelengths of electromagnetic waves. Different wavelengths can cause either gamma ray, x-ray, ultraviolet, infrared, micro, or radio waves, depending on how short or long they are. There is also a small portion of the spectrum that take the form of visible light, but a majority of it is invisible to the human eye. Click the link below to watch a video for a brief introduction.

Gamma Rays

Gamma ray waves have the highest frequency (higher than 3 x 1019 Hz) and the lowest wavelength (less than .01 nanometers) of all electromagnetic waves. These waves cannot be seen or felt, and are the product of radioactive atoms, but they have proven to be very useful. Gamma rays are used to kill cancer cells in patients, as well as to sterilize medical equipment. However, overexposure is very dangerous, and can cause an abnormality in cells that could lead to the forming of cancerous tumors. Pictured to the left is an image of the bursts of gamma rays that have been observed in space.

X-rays

X-rays have the second highest frequency (3 x 1016 - 3 x 1019 Hz) and the second lowest wavelength (.01 to 10 nm) on the electromagnetic spectrum. Like gamma rays, they cannot be seen or felt, and they're also used in the medical field. You've probably heard of someone having their x-ray taken, or maybe had one taken yourself. That's because x-rays are used to get pictures of bones in order to address possible fractures or breaks in them, as x-rays will pass easily through soft tissue like your skin and organs, but have a much harder time passing through hard surfaces like your bones. The reflections of the x-rays are read and used to create a picture of your skeleton. However, also like gamma rays, high exposure to these waves can cause cancer, which is why such care is protective care is taken when using them for medical purposes.

Ultraviolet Waves

Ultraviolet waves have a frequency of 7.5 x 1014 - 3 x 1016 Hz, and a wavelength of between 10 and 310 nanometers, landing it third highest and lowest, respectively, on the spectrum. As well as being used in things like sunbeds, fluorescent lights, and security pens, ultraviolet waves are naturally found in sunlight. Ultraviolet, or UV, radiation is what you protect against with sunscreen and sunglasses. Although they can't be seen or felt, our bodies naturally respond to the waves by manufacturing melanin, a sort of pigment, to protect your deep tissue and organs from the waves, as they can cause cancer in the case of overexposure, which is why you get tan after spending a day in the sun.

Visible Light

We can only see a small part of the electromagnetic spectrum, a portion called visible light, between the frequencies of 4 x 1014 and 7.5 x 1014 Hz and the wavelengths of 400 and 700 nanometers. This small portion creates the colors that we know and love, from red, with the longest wavelength, to violet, with the shortest wavelength. These different wavelengths are why we can filter white light through a prism to create a rainbow; the different wavelengths refract through the glass in slightly different ways. The same principle is what is responsible for seeing rainbows after it rains, the water acting the same as the glass of a prism.

Infrared

Infrared waves are what makes the technology for toasters and ovens possible. With a frequency of 3 x 1011 - 4 x 1014 Hz and a wavelength of 710 nm - 1 mm, we can feel infrared waves as heat. But they don't just work to help you make a toast! Infrared waves are used to create optical fiber technology, which is used in a wide range of things, from military drones and trains to decorative Christmas lights. Infrared is also used to create thermal vision. As we feel infrared waves as heat, devices that can pick up the waves can tell you the temperature of whatever it's viewing (a thermal vision image is pictured to the left).

Microwaves

Microwaves, besides, obviously, being used in microwaves by using their energy to heat up food, were crucial in the creation of a good deal of important technology. Their frequency of 3 x 109 - 3 x 1011 Hz and their wavelength of 1 - 100 millimeters enable a portion of them to be able to pass through the earth's atmosphere in order to reach satellites and other spacecrafts, which creates a way for communication between those on earth and the astronaut during space travel, as well as being able to transmit mobile phone signals.

Radio Waves

With the lowest frequencies of less than 3 x 1019 Hz and highest wavelengths of more than 1 millimeter, radio waves are necessary for many of our daily activities. Being very susceptible to diffraction and able to be transmitted over uneven terrain, they are used to transmit television programs, as well as radio programs. Those waves with low frequencies can even be reflected off the ionosphere and back down to earth in order to reach very far distances, bypassing the usual problems caused by the curve of the earth.