Page 74 & 75 Electromagnetic Spectrum |
What Is an Electromagnetic Wave?
You have seen waves travel in water, ropes, and springs. You have heard sound waves that travel through air and water. All these waves have two things in common—they transfer energy and they also require a medium through which to travel. But electromagnetic waves can transfer energy without a medium. An electromagnetic wave is a transverse wave that transfers electrical and magnetic energy. An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.
Energy
The energy that is transfered through space by electromagnetic waves is called electromagnetic radiation. Electromagnetic waves do not require a medium, so they can transfer energy through a vacuum, or empty space. This is why you can see the sun and stars—their light reaches Earth through the vacuum of space.
Speed
All electromagnetic waves travel at the same speed in a vacuum—about 300,000 kilometers per second. This speed is called the speed of light. At this speed, light from the sun takes about 8 minutes to travel the 150 million kilometers to Earth. When light waves travel through a medium such as air, they travel more slowly. But the speed of light waves in air is still about a million times faster than the speed of sound waves in air.
All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies. Radiation in the wavelengths that your eyes can see is called visible light. But only a small portion of electromagnetic radiation is visible light. The rest of the wavelengths are invisible. Your radio detects radio waves, which have much longer wavelengths than visible light. X-rays, on the other hand, are waves with much shorter wavelengths than visible light.
You have seen waves travel in water, ropes, and springs. You have heard sound waves that travel through air and water. All these waves have two things in common—they transfer energy and they also require a medium through which to travel. But electromagnetic waves can transfer energy without a medium. An electromagnetic wave is a transverse wave that transfers electrical and magnetic energy. An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.
Energy
The energy that is transfered through space by electromagnetic waves is called electromagnetic radiation. Electromagnetic waves do not require a medium, so they can transfer energy through a vacuum, or empty space. This is why you can see the sun and stars—their light reaches Earth through the vacuum of space.
Speed
All electromagnetic waves travel at the same speed in a vacuum—about 300,000 kilometers per second. This speed is called the speed of light. At this speed, light from the sun takes about 8 minutes to travel the 150 million kilometers to Earth. When light waves travel through a medium such as air, they travel more slowly. But the speed of light waves in air is still about a million times faster than the speed of sound waves in air.
All electromagnetic waves travel at the same speed in a vacuum, but they have different wavelengths and different frequencies. Radiation in the wavelengths that your eyes can see is called visible light. But only a small portion of electromagnetic radiation is visible light. The rest of the wavelengths are invisible. Your radio detects radio waves, which have much longer wavelengths than visible light. X-rays, on the other hand, are waves with much shorter wavelengths than visible light.
Because the speed of all electromagnetic waves is the same, as the wavelength decreases, the frequency increases. Waves with the longest wavelengths have the lowest frequencies. Waves with the shortest wavelengths have the highest frequencies. The amount of energy carried by an electromagnetic wave increases with frequency. The higher the frequency of a wave, the higher its energy.The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency. The electromagnetic spectrum is made up of radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and gamma rays.