Electromagnetic Spectrum

What is an electromagnetic wave?

Electromagnetic Waves They are transverse waves. Electromagnetic Spectrum –the range of electromagnetic waves placed in order of increasing frequency.

EM Waves EM Waves travel at the speed of light. c = 300,000,000 m/s (in vacuum) EM waves require no medium. Light waves are a part of the electromagnetic spectrum.

Electromagnetic Spectrum ROYGBV

Radio Waves Have the longest wavelengths and the lowest frequencies. A radio picks up radio waves sent out from towers and convert it to sound waves. These waves can be longer than a football field or as short as a football. Objects in space, such as planets and comets, giant clouds of gas and dust, and stars and galaxies, emit light at many different wavelengths. Some of the light they emit has very large wavelengths - sometimes as long as a mile!. These long waves are in the radio region of the electromagnetic spectrum. MRI’s also use radio waves.

They also carry signals for your TV and cell phones. But radio waves are also emitted by other things such as stars and gases in space.

Microwaves Microwaves are good for transmitting information from one place to another. Microwaves in space are used to learn about the structure of nearby galaxies. Microwaves have wavelengths that can be measured in centimeters! The longer microwaves, those closer to a foot in length, are the waves which heat our food in a microwave oven. Microwave energy can penetrate haze, light rain and snow, clouds, and smoke.

Microwaves can be used in remote sensing, microwave ovens, and radar. Microwave ovens transfer energy to the water in the food. This causes the molecules to vibrate which creates the heating of the food.

Infrared Infrared waves are thermal. Our skin emits infrared waves. This is why we can be seen in the dark by someone using thermal goggles. The heat that we feel from sunlight, a fire, a radiator or a warm sidewalk is infrared. The temperature-sensitive nerve endings in our skin can detect the difference between inside body temperature and outside skin temperature. You can feel the longest ones as warmth on your skin TV remotes use infrared.

TV remotes use infrared waves. In space, Infrared waves help to map the dust between stars.

Visible Light Visible light waves are the only electromagnetic waves we can see. These waves are seen as the colors of the rainbow. Each color has a different wavelength and frequency. When all the waves are seen together, they make white light. When white light shines through a prism, the white light is broken apart into the colors of the visible light spectrum. Water vapor in the atmosphere can also break apart wavelengths creating a rainbow.

Red has the longest wavelength and lowest frequency Violet has the shortest wavelength and highest frequency. The Sun is a natural source for visible light waves. Our eyes see the reflection of sunlight off the objects around us.

Ultraviolet The Sun is a source of UV rays. Some ultraviolet waves from the Sun gets through Earth's atmosphere, most of them are blocked by the Ozone layer. Though these waves are invisible to the human eye, some insects, like bumblebees, can see them!

Used to kill bacteria and the sterilization of equipment. UV causes your skin to produce vitamin D (good for teeth and bones) Too much UV can cause skin cancer. Some insects, like bumblebees, can see the UV waves.

X-Rays Carry a great amount of energy and can travel through most matter. The Earth's atmosphere is thick enough that virtually no X-rays get through from outer space.

Hot gases in the Universe also emit X-rays Bones and teeth absorb x-rays. The light part of an x-ray indicates where the x-ray was absorbed. X-Rays are used by engineers to check for tiny cracks in structures.

Gamma-Rays Gamma-rays have the smallest wavelengths and the highest frequency. They have greatest amount of energy and pass through the most materials.

Radioactive materials can emit gamma-rays. They are also produced by supernovas, nuclear explosions, and the destruction of atoms. Gamma-rays can kill living cells, such as cancer cells.