Updated On: Share This Video Whatsapp. Text Solution. Solution :. Very Important Questions. FAQs on Electromagnetic Wave. When you get an X-ray taken at a hospital, X-ray sensitive film is put on one side of your body, and X-rays are shot through you.
At a dentist, the film is put inside your mouth, on one side of your teeth, and X-rays are shot through your jaw, just like in this picture. It doesn't hurt at all - you can't feel X-rays. Because your bones and teeth are dense and absorb more X-rays then your skin does, silhouettes of your bones or teeth are left on the X-ray film while your skin appears transparent.
Metal absorbs even more X-rays - can you see the filling in the image of the tooth? When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film. This is an X-ray photo of a one year old girl. Can you see the shadow of what she swallowed? We use satellites with X-ray detectors on them to do X-ray astronomy. In astronomy, things that emit X-rays for example, black holes are like the dentist's X-ray machine, and the detector on the satellite is like the X-ray film.
X-ray detectors collect individual X-rays photons of X-ray light and things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them. To the right is an image of a real X-ray detector. It looks very different from anything you might see at a dentist's office!
Astrophysical sources of X-rays include plasmas with temperatures of 1 to million degrees Celcius, such as the solar corona , supernova remnants and gas in galaxy clusters. In addition to this blackbody radiation from hot gas, high-energy events involving charged particles moving at high speeds within a magnetic field can also generate X-rays.
By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds and aircraft. A Doppler shift in the radar echo can determine the speed of a car or the intensity of a rainstorm. Sophisticated radar systems can map the Earth and other planets, with a resolution limited by wavelength.
The shorter the wavelength of any probe, the smaller the detail it is possible to observe. A maser is a device similar to a laser, which amplifies light energy by stimulating photons. The maser, rather than amplifying visible light energy, amplifies the lower-frequency, longer-wavelength microwaves and radio frequency emissions. Infrared IR light is EM radiation with wavelengths longer than those of visible light from 0. Distinguish three ranges of the infrared portion of the spectrum, and describe processes of absorption and emission of infrared light by molecules.
Infrared IR light is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 0. This range of wavelengths corresponds to a frequency range of approximately GHz to THz, and includes most of the thermal radiation emitted by objects near room temperature. Infrared light is emitted or absorbed by molecules when they change their rotational-vibrational movements.
The infrared part of the electromagnetic spectrum covers the range from roughly GHz 1 mm to THz nm. It can be divided into three parts: It can be divided into three parts:. Observations of astronomical UV sources must be done from space. Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation. Heat is energy in transient form that flows due to temperature difference. Unlike heat transmitted by thermal conduction or thermal convection, radiation can propagate through a vacuum.
The concept of emissivity is important in understanding the infrared emissions of objects. This is a property of a surface which describes how its thermal emissions deviate from the ideal of a black body.
As stated above, while infrared radiation is commonly referred to as heat radiation, only objects emitting with a certain range of temperatures and emissivities will produce most of their electromagnetic emission in the infrared part of the spectrum. However, this is the case for most objects and environments humans encounter in our daily lives.
Humans, their surroundings, and the Earth itself emit most of their thermal radiation at wavelengths near 10 microns, the boundary between mid and far infrared according to the delineation above.
The range of wavelengths most relevant to thermally emitting objects on earth is often called the thermal infrared. Many astronomical objects emit detectable amounts of IR radiation at non-thermal wavelengths. Infrared radiation can be used to remotely determine the temperature of objects if the emissivity is known.
This is termed thermography, mainly used in military and industrial applications but the technology is reaching the public market in the form of infrared cameras on cars due to the massively reduced production costs.
Applications of IR waves extend to heating, communication, meteorology, spectroscopy, astronomy, biological and medical science, and even the analysis of works of art.
Visible light is the portion of the electromagnetic spectrum that is visible to the human eye, ranging from roughly to nm. Visible light, as called the visible spectrum, is the portion of the electromagnetic spectrum that is visible to can be detected by the human eye. A typical human eye will respond to wavelengths from about to nm 0. In terms of frequency, this corresponds to a band in the vicinity of — THz.
A light-adapted eye generally has its maximum sensitivity at around nm THz , in the green region of the optical spectrum. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths.
Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules.
The receivers or detectors of light largely utilize electronic transitions. We say the atoms and molecules are excited when they absorb and relax when they emit through electronic transitions. Visible Spectrum : A small part of the electromagnetic spectrum that includes its visible components. The divisions between infrared, visible, and ultraviolet are not perfectly distinct, nor are those between the seven rainbow colors.
The figure above shows this part of the spectrum, together with the colors associated with particular pure wavelengths.
Red light has the lowest frequencies and longest wavelengths, while violet has the highest frequencies and shortest wavelengths. Blackbody radiation from the Sun peaks in the visible part of the spectrum but is more intense in the red than in the violet, making the Sun yellowish in appearance. Colors that can be produced by visible light of a narrow band of wavelengths monochromaticlight are called pure spectral colors.
Quantitatively, the regions of the visible spectrum encompassing each spectral color can be delineated roughly as:. Note that each color can come in many shades, since the spectrum is continuous. The human eye is insensitive to electromagnetic radiation outside this range. By definition any images presented with data recorded from wavelengths other than those in the visible part of the spectrum such as IR images of humans or animals or astronomical X-ray images are necessarily in false color.
An example of this phenomenon is that clean air scatters blue light more than red wavelengths, and so the midday sky appears blue. The optical window is also called the visible window because it overlaps the human visible response spectrum. This allows visible light to heat the surface. The surface of the planet then emits energy primarily in infrared wavelengths, which has much greater difficulty escaping and thus causing the planet to cool due to the opacity of the atmosphere in the infrared.
Plants, like animals, have evolved to utilize and respond to parts of the electromagnetic spectrum they are embedded in. In plants, algae, and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth such as humans and animals. The portion of the EM spectrum used by photosynthesic organisms is called the photosynthetically active region PAR and corresponds to solar radiation between and nm, substantially overlapping with the range of human vision.
Ultraviolet UV light is electromagnetic radiation with a wavelength shorter than that of visible light in the range 10 nm to nm.
It is so-named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet. These frequencies are invisible to humans, but visible to a number of insects and birds. It can cause chemical reactions, and causes many substances to glow or fluoresce. Most ultraviolet is classified as non-ionizing radiation.
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