5.2 & 5.3 Flashcards
Objects in the universe send out an enormous range of electromagnetic radiation. Scientists call this range the ………….. …………., which they have divided into a number of categories.
electromagnetic spectrum
Electromagnetic radiation with the shortest wavelengths, no longer than 0.01 nanometer, is categorized as …………. ………. (1 nanometer = ……….. meters;
gamma rays / 10–9
Because gamma rays carry a lot of energy, they can be dangerous for living tissues. Gamma radiation is generated deep in the interior of stars, as well as by some of the most violent phenomena in the universe, such as the deaths of stars and the merging of stellar corpses. Gamma rays coming to Earth are absorbed by our atmosphere before they reach the ground
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Electromagnetic radiation with wavelengths between …….. nanometer and ……… ………… is referred to as X-rays.
0.01 / 20 / nanometers
ultraviolet light is sometimes called “…….. ……….” because our eyes cannot see it. Ultraviolet radiation is mostly blocked by the ……….. layer of Earth’s atmosphere, but a small fraction of ultraviolet rays from our Sun do penetrate to cause sunburn or, in extreme cases of overexposure, skin cancer in human beings.
black light / ozone
Electromagnetic radiation with wavelengths between roughly ……….. and ………. ……… is called visible light because these are the waves that human vision can perceive. This
400 / 700 nm
A heat lamp radiates mostly …………. radiation, and the nerve endings in our skin are sensitive to this band of the electromagnetic spectrum.
infrared
After infrared comes the familiar microwave, used in short-wave communication and microwave ovens. (Wavelengths vary from ……. ……….. to …….. …….. and are absorbed by water vapor, which makes them effective in heating foods.)
1 millimeter / 1 meter
Some astronomical objects emit mostly infrared radiation, others mostly visible light, and still others mostly ultraviolet radiation. What determines the type of electromagnetic radiation emitted by the Sun, stars, and other dense astronomical objects? The answer often turns out to be their ……………
temperature
A solid is composed of molecules and atoms in continuous vibration: they move back and forth in place. The hotter the solid or gas, the more ………… the motion of its molecules or atoms. The temperature of something is thus a measure of the ………. ………. energy of the particles that make it up.
rapid / average motion
This motion at the microscopic level is responsible for much of the electromagnetic radiation on Earth and in the universe.
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In science, the word …………. means the energy coming off per second (and it is typically measured in …………, which you are probably familiar with from buying lightbulbs).
power / watts
The wavelength at which maximum power is emitted can be calculated according to the equation ……………………..
where the wavelength is in nanometers (one billionth of a meter) and the temperature is in K (the constant 3 x 10^6 has units of nm × K). This relationship is called ……………
Wien’s law
The average temperature at the surface of the Sun, which is where the radiation that we see is emitted, turns out to be ………………
For the Sun, the wavelength at which the maximum energy is emitted is ………. nanometers, which is near the middle of that portion of the electromagnetic spectrum called visible light.
5800 K.
520
What we usually measure from a large object like a star is the …………. ……………, the power emitted per square meter.
energy flux
This relationship is known as the Stefan-Boltzmann law and can be written in the form of an equation as
where F stands for the energy flux (in units of watts per square meter), T is given in Kelvins, and σ (Greek letter sigma) is a constant number (…………..).
5.67 × 10-8
refract (bent)
كسر أشعة الشمس
……………….. and ………….. of light are the basic properties that make possible all optical instruments
Reflection / refraction
In 1672, in the first paper that he submitted to the Royal Society, Sir ……….. ………… described an experiment in which he permitted sunlight to pass through a small hole and then through a prism. Newton found that sunlight, which looks white to us, is actually made up of a mixture of all the colors of the rainbow
Isaac Newton
With Prism, The violet light is bent more than the red. This phenomenon is called …………….. and explains Newton’s rainbow experiment.
dispersion
Because this array of colors is a spectrum of light, the instrument used to disperse the light and form the spectrum is called a …………………
spectrometer
What are the three types of spectra?
- continuous spectrum
- absorption spectrum
- emission spectrum
A ………… ………… (formed when a solid or very dense gas gives off radiation) is an array of all wavelengths or colors of the rainbow. A continuous spectrum can serve as a backdrop** from which the atoms of much less dense gas can **absorb light.
continuous spectrum
A dark line, or ……….. …………., consists of a series or pattern of dark lines—missing colors—superimposed upon the continuous spectrum of a source.
superimposed: to put especially a picture, words, etc. on top of something else, especially another picture, words, etc., so that what is in the lower position can still be seen, heard, etc.:
absorption spectrum
A bright line, or ……….. ………., appears as a pattern or series of bright lines; it consists of light in which only certain discrete wavelengths are present.
emission spectrum
When we have a hot, thin gas, each particular chemical element or compound produces its own characteristic pattern of ……………. ………..—its ………… …………
No two types of atoms or molecules give the same patterns. In other words, each particular gas can absorb or emit only certain ………….. of the light peculiar to that gas.
spectral lines / spectral signature
wavelengths
absorption spectra occur when passing white light through a cool, thin gas. The temperature and other conditions determine whether the lines are bright or dark (whether light is emitted or absorbed),
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