Electromagnetic radiation Essay Example for Free

Electromagnetic radiation Essay Electromagnetic waves are disturbances caused by the oscillation of charged particles. It consists of two parts, an electric field and a magnetic field oscillating perpendicular to each other. The wave is self-sustaining, and propagates at a direction perpendicular to both the electric field and magnetic field. There is a whole spectrum of electromagnetic waves. The ones with the longest wavelengths (range: 1 cm-1km) are the radio waves. After the radio waves, microwaves have the next longest wavelength (range: 1mm-10cm). Then, we have the infrared waves (range: 1 µm-1mm), followed by light (range: 400nm-700nm), ultraviolet rays (range: 1nm-100nm), x-rays (range: 0. 1nm-10nm), and gamma rays, which have the shortest wavelengths amongst the different electromagnetic radiations (range: 0. 01nm-0. 1nm). b. How you determine the temperature, composition, and motion of an object from its light spectrum? Different elements emit and absorb light waves differently. Hence, when viewed through a spectroscope, different elements will have different spectral patterns. The object’s composition is obtained from noting which spectral lines are present or absent. We can also determine the density of the object depending on the amount of lines present in the spectrum. The more lines and the more continuous the spectrum, the denser is the material. On the other hand, the temperature of the object will affect the shapes spectral lines emitted by the object. If objects have high temperatures, their spectral lines will be broader, that is, it is spread over more frequencies than if it had lower temperature. To determine temperature, Finally, the Doppler Shift tells us the motion of the object, whether it is moving away or toward us, and with what speed. When the observed object is moving toward us, the spectral lines we observe occur at shorter wavelengths when we compare it to those measured in the laboratory. This is called â€Å"blueshifted. † On the other hand, if the object is moving away from us we observe the lines to occur at longer wavelengths. In this case we say that the lines are â€Å"redshifted. † The amount of shifting will determine the speed of motion. c. In what way do astronomers infer that the Sun’s energy comes from nuclear fusion reactions? How do we know it does not come from chemical burning? Even though both nuclear fusions and chemical reactions result in the release of energy, nuclear fusions release much more energy than chemical reactions. This is due to the nature of each reaction. Given that the energy that the sun produces is extremely high, it is impossible that chemical reactions are fuelling it, for if that were the case, then the sun will not be producing enough energy to sustain life on Earth. If it were chemical reactions powering it, it would be producing roughly one-millionth of the energy it is producing now. d. Explain how the Sun produces energy by nuclear fusion. Because of the amount of matter present in the sun, it is in danger of imploding. What keeps this from happening, however, is the nuclear fusion that occurs in its core, which is so hot because of the pressure from its mass that is being pulled inwards by gravity. In the core, hydrogen nuclei are forced to come together. This fusion creates helium-4 and energy. Since the resulting He-4 atoms are less massive than the initial hydrogen atoms that fused together, the missing mass is what was transformed into energy. This is best explained by the most famous equation in Physics, E=mc2, which states the equivalence of mass and energy. e. When we look at stars in the sky, we see a wide range of brightness. Explain the factors that would make one star appear brighter than another. There are two factors that affect the brightness of stars in the sky. The first one is the inherent characteristic of the star, which dictates how absolutely bright or luminous it will be. The second factor that affects the way we see stars is their distance from the earth. The farther they are, the dimmer they would appear. This is because the light they emit would need to pass through interstellar matter that could disperse, absorb or reflect the light in different directions. f. Compare the Sun with other stars. The Sun is called such by virtue of its position, that is, it is in the center of the solar system. Technically, however, the sun is also a star. It differs from other stars in its size, temperature, age, and color. The Sun is a dwarf star, about 4. 5 billion years old, and is classified as â€Å"yellow,† which means that it has an average temperature of about 6000 K. Hotter stars are classified as blue-white, while cooler stars are red. g. Consider a star at the upper part of the main sequence (label it Star A) and a star in the lower part of the main sequence (label it Star B). Which is: 1) Larger? Star A 2) More luminous? Star A 3) More massive? Star A 4) Hotter? Star A h. Compare the life spans of low mass stars and high mass stars. Explain why they are different. The life span of low mass stars is longer than the life spans of high mass stars. The reason for this is that the higher the mass of the star, the more hydrogen is needed to undergo fusion to keep the star from collapsing under its own gravitational force. i. What would an imaginary terrestrial observer see as the Sun runs out of hydrogen? If life is confined to Earth when this happens, would life perish from heat or from cold? Explain. As the Sun runs out of hydrogen fuel, it will start consuming helium. This leads to the sun increasing in radius, eventually turning it into a red giant. When this happens, the sun will grow so large that it can engulf the earth. Life on Earth would perish from extreme heat. When the helium runs out, however, the sun will shrink to a white dwarf. The reason for this is that the sun is too small to continue burning elements larger than helium. j. What kind of stars eventually become white dwarfs? What kind eventually become supernovae? What will be the ultimate fate of the Sun? Why? A white dwarf is an extremely dense star, with the mass of the sun and the size of the earth. It is composed of the remnants of stellar matter, which is mostly carbon and oxygen. In order to turn into a white dwarf, stars need to have a size of about 0. 07-10 times that of the sun. On the other hand, a supernova is formed when a massive star consumes all of its nuclear fuel and thus collapses under its gravitational field. Because of the high gravitational force that causes its collapse, the dead star suddenly explodes. A star that is about 8-10 times more massive than the sun will end its life as a supernova. The ultimate fate of the sun is to become a white dwarf. The reason for this is that the sun is not very massive to turn into a supernova, thus lacking the critical mass that would cause it to collapse under its own weight.