Ultraviolet Radiation - Definition of Science Terms

Ultraviolet radiation is another name for ultraviolet light. It is a part of the spectrum outside the visible range, just beyond the visible violet portion. Key Takeaways: Ultraviolet Radiation Ultraviolet radiation is also known as ultraviolet light or UV.It is light with a shorter wavelength (longer frequency) than visible light, but longer wavelength than x-radiation. It has a wavelength between 100 nm and 400 nm.Ultraviolet radiation is sometimes called black light because it is outside range of human vision. Ultraviolet Radiation Definition Ultraviolet radiation is electromagnetic radiation or light having a wavelength greater than 100 nm but less than 400 nm. It is also known as UV radiation, ultraviolet light, or simply UV. Ultraviolet radiation has a wavelength longer than that of x-rays but shorter than that of visible light. Although ultraviolet light is energetic enough to break some chemical bonds, it is not (usually) considered a form of ionizing radiation. The energy absorbed by molecules can provide the activation energy to start chemical reactions and may cause some materials to fluoresce or phosphoresce. The word ultraviolet means beyond violet. Ultraviolet radiation was discovered by the German physicist Johann Wilhelm Ritter in 1801. Ritter noticed invisible light beyond the violet portion of the visible spectrum darkened silver chloride treated paper more quickly than violet light. He called the invisible light oxidizing rays, referring to the chemical activity of the radiation. Most people used the phrase chemical rays until the end of the 19th century, when heat rays became known as infrared radiation and chemical rays became ultraviolet radiation. Sources of Ultraviolet Radiation About 10 percent of the light output of the Sun is UV radiation. When sunlight enters the Earths atmosphere, the light is about 50% infrared radiation, 40% visible light, and 10% ultraviolet radiation. However, the atmosphere blocks about 77% of solar UV light, mostly in shorter wavelengths. Light reaching the Earths surface is about 53% infrared, 44% visible, and 3% UV. Ultraviolet light is produced by black lights, mercury-vapor lamps, and tanning lamps. Any sufficiently hot body emits ultraviolet light (black-body radiation). Thus, stars hotter than the Sun emit more UV light. Categories of Ultraviolet Light Ultraviolet light is broken into several ranges, as described by ISO standard ISO-21348: Name Abbreviation Wavelength (nm) Photon Energy (eV) Other Names Ultraviolet A UVA 315-400 3.10–3.94 long-wave, black light (not absorbed by ozone) Ultraviolet B UVB 280-315 3.94–4.43 medium-wave (mostly absorbed by ozone) Ultraviolet C UVC 100-280 4.43–12.4 short-wave (completely absorbed by ozone) Near ultraviolet NUV 300-400 3.10–4.13 visible to fish, insects, birds, some mammals Middle ultraviolet MUV 200-300 4.13–6.20 Far ultraviolet FUV 122-200 6.20–12.4 Hydrogen Lyman-alpha H Lyman-ÃŽ ± 121-122 10.16–10.25 spectral line of hydrogen at 121.6 nm; ionizing at shorter wavelengths Vacuum ultraviolet VUV 10-200 6.20–124 absorbed by oxygen, yet 150-200 nm can travel through nitrogen Extreme ultraviolet EUV 10-121 10.25–124 actually is ionizing radiation, although absorbed by the atmosphere Seeing UV Light Most people cannot see ultraviolet light, however, this is not necessarily because the human retina cant detect it. The lens of the eye filters UVB and higher frequencies, plus most people lack the color receptor to see the light. Children and young adults are more likely to perceive UV than older adults, but people missing a lens (aphakia) or who have had a lens replaced (as for cataract surgery) may see some UV wavelengths. People who can see UV report it as a blue-white or violet-white color. Insects, birds, and some mammals see near-UV light. Birds have true UV vision, as they have a fourth color receptor to perceive it. Reindeer are an example of a mammal that sees UV light. They use it to see polar bears against snow. Other mammals use ultraviolet to see urine trails to track prey. Ultraviolet Radiation and Evolution Enzymes used to repair DNA in mitosis and meiosis are believed to have developed from early repair enzymes that were designed to fix damage caused by ultraviolet light. Earlier in Earths history, prokaryotes could not survive on the Earths surface because exposure to UVB caused adjacent thymine base pair to bind together or form thymine dimers. This disruption was fatal to the cell because it shifted the reading frame used to replicate genetic material and produce proteins. Prokaryotes that escaped protective aquatic life developed enzymes to repair thymine dimers. Even though the ozone layer eventually formed, protecting cells from the worst of the solar ultraviolet radiation, these repair enzymes remain. Sources Bolton, James; Colton, Christine (2008). The Ultraviolet Disinfection Handbook. American Water Works Association. ISBN 978-1-58321-584-5.Hockberger, Philip E. (2002). A History of Ultraviolet Photobiology for Humans, Animals and Microorganisms. Photochemistry and Photobiology. 76 (6): 561–569. doi:10.1562/0031-8655(2002)0760561AHOUPF2.0.CO2Hunt, D. M.; Carvalho, L. S.; Cowing, J. A.; Davies, W. L. (2009). Evolution and spectral tuning of visual pigments in birds and mammals. Philosophical Transactions of the Royal Society B: Biological Sciences. 364 (1531): 2941–2955. doi:10.1098/rstb.2009.0044

The Atomic Bomb During World War II - 1924 Words

During World War II, Japan refused to surrender to the Allied Powers due to the fact that the fate of their leader, Michinomiya Hirohito, was uncertain. The United States wanted to end the war quickly and prevent lives being taken because of an invasion of Japan. This led to the creation of the atomic bomb with the Manhattan Project. President Truman’s order to drop the atomic bomb on Japan ended the war. However, using the atomic bomb resulted in conflicts such as the Cold War, and present day problems such as the Iran Deal and North Korea. The creation of the atomic bomb began with the Manhattan Project. During World War II, the United States were fearful that Germany would use a nuclear weapon so they created the Manhattan Project†¦show more content†¦On August 6th, 1945 the United States dropped a nuclear bomb called Little Boy in the town of Hiroshima. The Little Boy was the heaviest bomb at the time weighing 9,700 pounds and with a length of 10 feet. The task of dropping the first atomic bomb was carried out by the 509th Composite Group (Little Boy and Fat Man Web). However the dropping of Little Boy caused major casualties, the bombing of Hiroshima killed 180,000 people (Kennedy, Chapter 36). Three days later, on August 9th, 1945 the second and final atomic bomb that would ever be dropped on a city was called Fat Man which destroyed Nagasaki casing 80,000 deaths (Kennedy Chapter 36). The Manhattan Project was eventually absorbed into the Atomic Energy Commission (AEC). After the bombs destroyed Hiroshima and Nagasaki other nations scrambled to get their hands on weapons of mass destruction. This would eventually lead up to the Cold War between the Soviet Union and the United States. Even though the Manhattan Project is now gone, the terrible consequences of its invention of the atomic bomb still linger today (â€Å"Key Issues: Nuclear Weapons: History: Pre Cold War: Manhattan Project† Web; â€Å"Little Boy and Fat Man† Web). The Cold War was a conflict between the United States and the Soviet Union that occurred from 1947 to 1991. There are many reasons on why the Cold War occurred between the two countries such as: the conflict between communism and capitalism, which country

Family Tree free essay sample

My grandparents from my mother’s side of the family were both born in China and resided in a small town their entire life. My grandmother—Po Po, goes by the name of Ling Tan; and my grandfather—Gung Gung, is called Chau Yi Chen. Both of them lived in the same village and were tied together through arrange marriage which is a very popular tradition in China. Due to China’s one child policy, my grandfather grew up with no siblings because it was illegal to give birth to more than one child. Unless the family is within the minority and falls under certain circumstances, the family would be fined heavily if they give birth to addition children. Grandfather Chau Yi worked as a farmer to help support his family; and Grandmother Ling was born in a middle class family and had an older brother—Tim Chi Tan. Being a middle class family had given her family the ability to pay off their fine for having a second child. We will write a custom essay sample on Family Tree or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Granduncle Tim Chi left home in 1958 hoping for a better future in life, but he has never returned home ever since—neither did he contact the family. Therefore, I do not have much info about him and my mother would forbid me asking. Nevertheless, my grandmother grew up helping her parents in a small Chinese restaurant until she married my grandfather. After my grandparents were married for two years, they gave birth to my mother named Yan Ru Chen and a younger brother named Chang Yi Chen. Uncle Chang Yi worked at a restaurant as a waiter during daytime and a delivers newspaper early in the morning. Uncle Chang Yi left home in 1984 in attempts to seek a better life by swimming across the border to Hong Kong. Unfortunately, he failed his first attempt and was deported back home. Knowing that the opportunities in China are very limited, my grandmother cannot stand seeing her son’s potential to succeed trample in waste. She exhausted her savings to payoff generals for my uncle to reach Hong Kong safely—undocumented. His second attempt to leave home was a success, and a new chapter of his life begins. My uncle currently resides in Hong Kong and is happily married with two daughters. Furthermore, my grandparents from my father’s side of the family were also born in China and lived in the Guangdong Province their entire life. My grandma—Ma Ma, Hua Li Li, and grandpa—Yei Yei, Chung Yu, both grew up as the only child in their family and were raised in the lower class. They were neighbors and knew each other ever since their early adolescent years. My grandma grew up working in her parent’s grocery store selling fruits and vegetables as a living. My grandpa worked in a farmer market selling pork and fish and supported his parents. My grandparents were married in 1945 and 3 years later they had their first and only child which is my father named Shiu Ki Yu. My father left home around 1974 to work in the navy for 5 years and later immigrated to United States after hearing how beautiful it is and how much freedom you can have. My mother immigrated to the United States in 1987 and was introduced to my father by an old friend from China. The first and only city both of my parents lived in the United States is San Francisco. My father worked as a chief in Chinatown and my mother worked as seamstress on Third Street of market. In 1990, they gave birth to my older sister and two years later I was born. Another two years later we welcomed a younger brother to our family. Both sides of my grandparents did not want to move to America because they were afraid to start a new lifestyle, old of age, and language will be a barrier for them. At the same time, my parents were not able to support them while being paid a low wage and trying to feed their three kids. Currently, my parents are retired while my siblings and I are pursuing our college education in California. A new life soon awaits as we all look forward to being the first in the family to pursue a higher education and to graduate college.