Hi there! In the previous lesson, we were able to describe the different regions of electromagnetic waves. In this video, we will be citing examples of its practical applications.
By the way, if you still haven't watched the previous lesson, You can pause this video and watch that one first to better understand our topic today. Radiation is the transmission of energy in the form of waves or particles through space or through a material medium. It may take such forms as light or tiny particles much too small to see. Visible light, the ultraviolet light we receive from the sun, transmission signals for TV and radio communications are all forms of radiation that are common in our daily lives.
These are all generally referred to as non ionizing radiation though at least some ultraviolet radiation is considered to be ionizing. Radiation particularly associated with nuclear medicine and the use of nuclear energy Along with x-rays is ionizing radiation, which means that the radiation has sufficient energy to interact with matter, especially the human body, and produce ions. Today, conversations, photos, and even music can be transmitted through air over thousands of miles because of radio waves. Wireless communication has become possible through transmission and reception of these radio waves.
If you may recall, radio waves can be transmitted through empty space. Radio waves have the longest wavelength in the electromagnetic spectrum. They are produced by making electrons vibrate in an antenna.
Medium and high frequency waves are used for broadcasting by local radio stations. In a radio station, sound is converted by a microphone into patterns of electric current variations called audio frequency or AF signals. High frequency radio waves called radio frequency or RF carriers can be modulated to match the electronic signal. In amplitude modulation or AM, The amplitude of the radio waves changes to match that of the audio frequency signal.
This is used in standard broadcasting because it can be sent over long distances. Very high frequency waves provide a higher quality of broadcasting, including stereo sound. In this process, instead of the amplitude of the RF carrier, It is the frequency of the waves that changes to match that of the signal.
This is called frequency modulation or FM. When the radio wave is received by the antenna of a radio or television, the pattern is converted back to its original form. The sound portions of most television broadcasts are carried as AM waves, while the picture portions are carried as FM waves.
They are used to transmit sound and picture information over long distances. Radiowaves have a very wide range of wavelengths. The whole region of the radio waves is divided into smaller regions of wave bands. Each wave band is allocated by law to a specific radio service.
Did you know? Frequency is an important characteristic of radio waves. AM broadcast frequency is about 1 million Hz. For example, when you tune in to your favorite AM radio station at 630 on the dial, the radio is tuning to the radio wave with a frequency of 630,000 Hz.
On the other hand, FM radio operates on 100 million Hz. So when you tune in to 101.1 FM, Your radio is tuning to 101,100,000 Hz. We know for a fact that radio waves travel in a straight line. Why then are we able to receive messages or information from other parts of the world?
Let's take a short review of some facts we learn in earth science. One layer of the atmosphere is composed of ionized gases. This layer is called the ionosphere. The high-frequency waves penetrate into the ionosphere and into space.
Therefore, communication satellites are used to reflect these waves back to Earth, which are then captured by the receiving antennas. Microwaves can penetrate the atmosphere of the Earth. This is the reason why they are used for satellite communications. Microwave signals are transmitted by an antenna to a satellite which amplifies and retransmits the signal to an antenna in another part of the world.
This is how we communicate with the rest of the world. Most communication satellites are used to send and receive radio signals for telephone services, while the rest are for television broadcasting, scientific research, and weather forecast. Microwaves have short wavelengths and are reflected by small objects. This property is used in radars.
Radar is an acronym for radio detection and ranging. A radar system consists of an antenna, transmitter, and a receiver. The antenna whirls around continuously to scan the surrounding area.
The transmitter sends out a narrow beam of microwaves in short pulses. A distant object reflects some of the signal back to the receiver. The direction to which the signal was received gives the direction of the object. The distance of the object can be calculated from the time lag between the transmitted pulse and the reflected pulse.
Have you noticed that a lot of people now resort to cable TV for news, entertainment, and educational programs? Cable TV is now used because of its wide range of channels and clearer sound and picture. Moreover, some cable companies provide internet access to users. So how does cable TV work?
Microwaves are used to transmit television news coverage from mobile broadcast vehicles back to the station. The news crew can also set up a small antenna. to send signals to a communication satellite.
This is how news are broadcasted and watched live around the world. A cell phone is a radio transmitter and receiver that uses microwaves. A cellular phone is a very sophisticated radio, but still a radio nonetheless.
It is today's answer to the emerging demand for mobile communication. Cellular phones depend on overlapping network of cells or areas of land several kilometers in diameter. Each cell has its tower that receives and sends microwave signals. In a microwave oven, food absorbs certain microwave frequencies very strongly.
The microwaves penetrate the food being heated. It will agitate the water molecules within the food. thus creating molecular friction which then produces heat that will cook it.
Infrared waves are in the lower middle range of frequencies in the electromagnetic spectrum. Infrared radiation lies beyond the red end of the visible light. The size of infrared waves ranges from a few millimeters down to microscopic lengths.
The longer wavelength infrared waves produce heat and include radiation emitted by fire, the sun, and other heat-producing objects. Shorter wavelength infrared rays do not produce much heat and are used in remote controls and imaging technologies. The amount and wavelength of radiation depend on temperature.
Below 500 degrees Celsius, an object emits only infrared radiation. Above 500 degrees Celsius. An object glows and emits both infrared and visible light.
The difference in color determine the differences in temperature. For example, shades of blue and green indicate regions of colder temperature, and red and yellow indicate warmer temperature. The human eye is not sensitive to the infrared light used by television remote controls. To send a signal to a television, remote controls often use a diode that emits light.
Some digital cameras have filters to block near-infrared light, but most can detect it. It shows up on the screen as if it were visible light. When you press a button on the remote control, the camera may show a pulsing light emitted by the remote. The following are some useful applications of infrared radiation.
Infrared photographs taken from a satellite with special films provide useful details of the vegetation on the Earth's surface. Infrared scanners are used to show the temperature variation of the body. This can be used for medical diagnosis.
Infrared remote controls are used in TVs and other electronic appliances. An infrared camera has a transmitter that sends out infrared pulses. And lastly, night vision goggles allow infrared vision to be seen.
Images to be produced in levels of light approaching total darkness. When white light passes through a prism, it is separated into its constituent colors. Red, orange, yellow, green, blue, indigo, and violet.
These colors do not distinctly separate, but they continuously change from red to violet. Red has the longest wavelength from among these colors, and violet has the shortest. Our eyes are sensitive to electromagnetic waves of wavelengths that range from 4 x 10 raised to negative 7th power meters to 7 x 10 raised to negative 7th power meters.
These are the range of wavelengths of white light. Thus, the spectrum of white light is the spectrum of white light. is therefore called the visible spectrum. Visible light is essential for photosynthesis. Photosynthesis is the process by which plants make food.
Forms of energy taken from the sun, used by plants and microorganisms millions of years ago, are locked up in coal and oil used as energy resources today. There are several ways in which a luminous object can be made to give off energy in the form of light. A luminous object can produce incandescent light, fluorescent light, and neon light. Incandescent light is a form of light produced by heat. They produce light when electricity is applied to them.
Inside the glass bulb is a thin wire filament. made of metal tungsten. Tungsten can be heated to over 2000 degrees Celsius without melting.
Fluorescent light is cooler and uses less energy than incandescent light. Instead of being used to build up heat, electrons in fluorescent lights are used to bombard molecules of gas kept at low pressure in a tube. The color that a fluorescent bulb produces depends on the phosphors used. Neon light can be seen in thin glass tubes of brightly colored lights. It is a cool light, similar to fluorescent light.
When electrons pass through the glass tubes filled with certain gases, light is produced. The most common type of gas used is neon gas, which produces bright red light. If If other gases are added, however, different colors are produced. Ultraviolet radiation lies just beyond the violet end of the visible spectrum. Ultraviolet waves have shorter wavelengths than the visible light and carry more energy.
The sun is our main source of ultraviolet radiation, but there are also artificial sources of UV light. Ultraviolet radiation in UV lamps are used by banks to check the signature on a passbook. The signature is marked on the passbook with fluorescent ink. It becomes visible when viewed under a UV lamp. These lamps are also used to identify fake banknotes.
UV radiation is also used in sterilizing water from drinking fountains. Some laundry detergents also contain fluorescent chemicals which glow in sunlight. This makes your shirt look whiter in daylight.
UV radiation in sunlight helps produce vitamin D in the skin and gives us a tanning effect. X-rays come just after the ultraviolet rays. They are of shorter wavelengths but carry higher energy than ultraviolet rays. X-rays are produced using an X-ray tube. They are emitted when fast-moving electrons hit the metal target.
X-rays were discovered by Willem Conrad Roentgen in 1895. Long wavelength X-rays can penetrate the flesh but not the bones. They are used in x-ray photography to help doctors look inside body. They are useful in diagnosing bone fractures and tumors. Short wavelength x-rays can penetrate even through metals. They are used in industry to inspect welded joints for faults.
Gamma rays lie at the other end of the electromagnetic spectrum. They are shortest in wavelength and highest in frequency. Gamma rays are emitted by only the most energetic cosmic objects such as pulsars, neutron stars, supernovas, and black holes.
Terrestrial sources include lightning, nuclear explosions, and radioactive decay. Gamma ray wavelengths are measured on the subatomic level and can actually pass through the empty space within an atom. Gamma rays can destroy living things.
Fortunately, the Earth's atmosphere absorbs any gamma rays that reach the planet. Gamma rays carry the highest amount of energy. Thus, they are more dangerous. They can also be blocked with lead and thick concrete.
Gamma rays are very strong that they can kill living cells. Gamma rays are used to treat cancer through the process called radiotherapy. They are also used for sterilization of drinking water.
Now let's wrap things up. Here's a table to summarize the applications and uses of each electromagnetic wave. Radiowaves are used in radio and television communication.
Microwaves are used in satellite communication, terrestrial communications, radar, and microwave ovens. Infrared rays are found in remote controls, infrared scanners, night vision goggles, camera autofocus, and thermograms. Visible light is important in photosynthesis in plants.
It can be used as artificial lighting, optical fibers in medical uses, and screens of electronic devices. Ultraviolet rays are used to sterilize water from drinking fountains and check signatures on a passbook. It's also used to identify fake banknotes. X-rays are used in the field of medicine and engineering.
Lastly, Gamma rays are also used in the medical and industrial fields. That's all for now. We will be discussing about the effects of electromagnetic radiation on living things and the environment in our next video so stay tuned.
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