Learn your Physics’ ABC here!
This edition’s topic: Electromagnetic waves
Radio waves Visible light.
Technology and Nature both give rise to these electromagnetic waves. From our daily vision to digital entertainment, these waves are constantly around us…
Radio waves
Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wavelike properties of light and similarities in electrical and magnetic observations. He then proposed equations that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed, making practical the use of radio waves to transfer information through space. Nikola Tesla and Guglielmo Marconi are credited with inventing systems to allow radio waves to be used for communication.
Radio waves have the longest wavelengths in the electromagnetic spectrum. Radio waves are used not only in radio broadcasting but in wireless telegraphy, telephone transmission, television, radar, navigation systems and telecommunications. Unlike microwaves, radio waves are able to go around obstructions due to their longer wavelengths.
The antennae on your television set receive the signal, in the form of electromagnetic waves that is broadcasted from the television station. It is then displayed on your television screen. Cellular phones also use radio waves to transmit information. These waves are much smaller that TV and FM radio waves.
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. By studying the radio waves originating from space, astronomers can learn about their composition, structure, and motion. Radio astronomy has the advantage that sunlight, clouds, and rain do not affect observations.
Radio telescopes are dishes made out of conducting metal that reflect radio waves to a focus point. Because the wavelengths of radio light are so large, a radio telescope must be physically larger than an optical telescope to be able to make images of comparable clarity. In order to make better and more clear (or higher resolution) radio images, radio astronomers often combine several smaller telescopes, or receiving dishes, into an array. Together, the dishes can act as one large telescope whose size equals the total area occupied by the array.
Although Radio waves have very low frequency and may seem harmless, it is still uncertain whether radio waves can do damage to our brain through over exposure of talking on the telephone.
Radio waves are constantly being used in more ways in technology that help make our lives better and more enjoyable
REFLECTION: On this study of radio waves, I realized that radio waves are used in more ways than I had imagined, such as in telecommunications. Before researching I thought they were only used in radios and not in others since they are weak and not strong enough to reach the satellites in space. However, now I know the radio waves can be used in many areas and are very vital in our telecommunication systems. Since radio waves have the tendency to cause damage to cells after a prolonged period of exposure, I will try to avoid using the phone for too long to avoid taking risks.
http://science.hq.nasa.gov/kids/imagers/ems/radio.html
http://en.wikipedia.org/wiki/Radio_waves
Visible light
http://science.hq.nasa.gov/kids/imagers/ems/visible.html
http://en.wikipedia.org/wiki/Visible_light
Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. 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. A typical human eye will respond to wavelengths from about 380 to 750nm, which falls within this region. Thus the vision we get everyday is from these rays, including all the wonderful sceneries in the world, all the cute little animals and all the graphics that we see…
Isaac Newton first discovered this visible spectrum of light. Newton observed that when a narrow beam of sunlight strikes the face of a glass prism at an angle, some is reflected and some of the beam passes into and through the glass, emerging as different colored bands. Newton hypothesized that light was made up of particles of different colors, and that the different colors of light moved at different speeds in transparent matter, with red light moving more quickly in glass than violet. The result is that red light refracts less sharply than violet as it passes through the prism, creating a spectrum of colors.
There are two types of color images that can be made from satellite data - true-color and false-color. To take true-color images, like this one, the satellite that took it used sensors to record data about the red, green, and blue visible light waves that were reflecting off the earth's surface. The data were combined later on a computer. The result is similar to what our eyes see.
A false-color image is made when the satellite records data about brightness of the light waves reflecting off the Earth's surface. These brightnesses are represented by numerical values - and these values can then be color-coded. Astronomers can even view a region of interest by using software to change the contrast and brightness on the picture
We are blind to many wavelengths of light. This makes it important to use instruments that can detect different wavelengths of light to help us to study the Earth and the Universe.
However, since visible light is the part of the electromagnetic spectrum that our eyes can see, our whole world is oriented around it. Still, there are many wavelengths of light that our eyes cannot detect. Many instruments that detect visible light can see father and more clearly than our eyes could alone. That is why we use satellites to look at the Earth, and telescopes to look at the Sky!