The Electromagnetic Spectrum
Table lists the wavelength and frequency ranges of the divisions of the . EM radiation in the visible part of the spectrum is scattered off all of the objects. What is the relationship between wavelength, frequency and energy? Young, hot stars produce a lot of ultraviolet light and bathe interstellar space with this. Radiation is energy that travels and spreads out as it goes – the visible light that The electromagnetic spectrum from lowest energy/longest wavelength (at the.
Since these are the longest waves, they have the lowest energy and are associated with the lowest temperatures.
Star Light, Star Bright -- Science Background
Radio wavelengths are found everywhere: Radio stations use radio wavelengths of electromagnetic radiation to send signals that our radios then translate into sound. These wavelengths are typically a few feet long in the FM band and up to yards or more in the AM band.
Radio stations transmit electromagnetic radiation, not sound. The radio station encodes a pattern on the electromagnetic radiation it transmits, and then our radios receive the electromagnetic radiation, decode the pattern and translate the pattern into sound.
Electromagnetic Spectrum - Wavelength, Frequency, And Energy, Wavelength Regions
New instrumentation and computer techniques of the late 20th century allow scientists to measure the universe in many regions of the electromagnetic spectrum. We build devices that are sensitive to the light that our eyes cannot see. Then, so that we can "see" these regions of the electromagnetic spectrum, computer image-processing techniques assign arbitrary color values to the light.
What is a light wave? Light is a disturbance of electric and magnetic fields that travels in the form of a wave. Imagine throwing a pebble into a still pond and watching the circular ripples moving outward. Like those ripples, each light wave has a series of high points known as crests, where the electric field is highest, and a series of low points known as troughs, where the electric field is lowest.
The wavelength is the distance between two wave crests, which is the same as the distance between two troughs. The number of waves that pass through a given point in one second is called the frequency, measured in units of cycles per second called Hertz.
The speed of the wave therefore equals the frequency times the wavelength. What is the relationship between frequency and wavelength? Wavelength and frequency of light are closely related.
The higher the frequency, the shorter the wavelength. Because all light waves move through a vacuum at the same speed, the number of wave crests passing by a given point in one second depends on the wavelength. That number, also known as the frequency, will be larger for a short-wavelength wave than for a long-wavelength wave.
The equation that relates wavelength and frequency is: For electromagnetic radiation, the speed is equal to the speed of light, c, and the equation becomes: What is the relationship between wavelength, frequency and energy?
The energy of a wave is directly proportional to its frequency, but inversely proportional to its wavelength. In other words, the greater the energy, the larger the frequency and the shorter smaller the wavelength. Given the relationship between wavelength and frequency described above, it follows that short wavelengths are more energetic than long wavelengths.
How are wavelength and temperature related? All objects emit electromagnetic radiation, and the amount of radiation emitted at each wavelength determines the temperature of the object.
Hot objects emit more of their light at short wavelengths, and cold objects emit more of their light at long wavelengths. The radiation temperature of an object is related to the wavelength at which the object gives out the most light. We call the amount of light emitted at a particular wavelength, the intensity. When you plot the intensity of light from an object at each wavelength, you trace out a smooth curve called a blackbody curve. For any temperature, the blackbody curve shows how much energy intensity is radiated at each wavelength, and the wavelength where the intensity peaks determines the color of that the object.
The intensity peak will be at shorter bluer wavelengths for hotter objects, and at longer redder wavelengths for cooler objects. Therefore, you can tell the temperature of a star or galaxy by its color because color is closely related to the wavelength at which its light intensity peaks. Blackbody curves, for objects of all temperatures, have a similar shape, as shown in the graphsbelow. However, the peak of the curve for a hotter object will be larger more intense than will the peak of the curve for a cooler object.
For example, the intensity difference between the peak of the curve for an object at 30, K and the peak of the curve for an object at K body temperature is a factor of 10 billion. This means that a star at 30, K puts out more energy by a factor of 10 billion than does a human at body temperature.
Because of the large intensity difference, it would be difficult to show both of these curves on the graph below without using logarithms. To plot blackbody curves with large intensity differences on the Heating Up page of Amazing Space's "Star Light, Star Bright", we have made the scale of the intensity axis adjust itself for each temperature change. How are temperature and color related? The amount of light produced by an object at each wavelength depends on the temperature of the object producing the light.
Stars hotter than the sun over 6, degrees C put out most of their light in the blue and ultraviolet regions of the spectrum. Until recently, the range was rarely studied and few sources existed for microwave energy at the high end of the band sub-millimeter waves or so-called terahertz wavesbut applications such as imaging and communications are now appearing.
Scientists are also looking to apply terahertz technology in the armed forces, where high-frequency waves might be directed at enemy troops to incapacitate their electronic equipment. Infrared radiation Main article: It can be divided into three parts: The lower part of this range may also be called microwaves or terahertz waves.
This radiation is typically absorbed by so-called rotational modes in gas-phase molecules, by molecular motions in liquids, and by phonons in solids. The water in Earth's atmosphere absorbs so strongly in this range that it renders the atmosphere in effect opaque. However, there are certain wavelength ranges "windows" within the opaque range that allow partial transmission, and can be used for astronomy.
Mid-infrared, from 30 to THz 10—2. Hot objects black-body radiators can radiate strongly in this range, and human skin at normal body temperature radiates strongly at the lower end of this region.
This radiation is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions. This range is sometimes called the fingerprint region, since the mid-infrared absorption spectrum of a compound is very specific for that compound. Physical processes that are relevant for this range are similar to those for visible light.
The highest frequencies in this region can be detected directly by some types of photographic film, and by many types of solid state image sensors for infrared photography and videography.
Visible radiation light Main article: Visible spectrum Above infrared in frequency comes visible light. The Sun emits its peak power in the visible region, although integrating the entire emission power spectrum through all wavelengths shows that the Sun emits slightly more infrared than visible light.
Visible light and near-infrared light is typically absorbed and emitted by electrons in molecules and atoms that move from one energy level to another. This action allows the chemical mechanisms that underlie human vision and plant photosynthesis. The light that excites the human visual system is a very small portion of the electromagnetic spectrum.
A rainbow shows the optical visible part of the electromagnetic spectrum; infrared if it could be seen would be located just beyond the red side of the rainbow with ultraviolet appearing just beyond the violet end.
White light is a combination of lights of different wavelengths in the visible spectrum. If radiation having a frequency in the visible region of the EM spectrum reflects off an object, say, a bowl of fruit, and then strikes the eyes, this results in visual perception of the scene.
The brain's visual system processes the multitude of reflected frequencies into different shades and hues, and through this insufficiently-understood psychophysical phenomenon, most people perceive a bowl of fruit. At most wavelengths, however, the information carried by electromagnetic radiation is not directly detected by human senses.
Natural sources produce EM radiation across the spectrum, and technology can also manipulate a broad range of wavelengths. Optical fiber transmits light that, although not necessarily in the visible part of the spectrum it is usually infraredcan carry information.
The modulation is similar to that used with radio waves. Ultraviolet radiation Main article: The wavelength of UV rays is shorter than the violet end of the visible spectrum but longer than the X-ray. UV is the longest wavelength radiation whose photons are energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.
Short wavelength UV and the shorter wavelength radiation above it X-rays and gamma rays are called ionizing radiationand exposure to them can damage living tissue, making them a health hazard. UV can also cause many substances to glow with visible light; this is called fluorescence.
At the middle range of UV, UV rays cannot ionize but can break chemical bonds, making molecules unusually reactive. Sunburnfor example, is caused by the disruptive effects of middle range UV radiation on skin cellswhich is the main cause of skin cancer.
UV rays in the middle range can irreparably damage the complex DNA molecules in the cells producing thymine dimers making it a very potent mutagen. However, most of the Sun's damaging UV wavelengths are absorbed by the atmosphere before they reach the surface. The higher energy shortest wavelength ranges of UV called "vacuum UV" are absorbed by nitrogen and, at longer wavelengths, by simple diatomic oxygen in the air.