Biology

Ultraviolet Rays INVESTIGATORY PROJECT IN BIOLOGY In partial fulfillment of project inBiologyBy………………………………ULTRAVIOLET RAYS________________________________SUBMITTED TO:DEPARTMENT OF BIOLOGYAL-FAROOK RESIDENTIAL SCHOOL [Affiliated to CBSE, New Delhi]2009-10Al Farook Residential School [Affiliated to CBSE, New Delhi]Farook college-673632 Laboratory certificateThis is to certify that the project work titled Is a bonafide record done by:Reg. No. ………………………………In partial fulfillment of the project in Biology during the year2013-2014 Mr.ABC Department of Botany Principal Mrs. #$&& Department of Zoology Certified that the candidate was examined by us in the project work/viva voce examination held at Al-farook residential school on………………………. Internal examiner External Examiner INTRODUCTION In the present 21stcentury world one does not need to say about ultra violet rays, it is the most talked about topic in this era. From the common man to academicians UV rays hold an important place.UV rays have been discussed for long around the world especially after the discovery of the hole in the ozone layer in 1990s.The hole meant the approaching death of our mother earth. A host of studies have been undertaken by many people and organizations such as the United Nations, GREENPEACE etc.Even when the world speaks much about this great calamity that has befallen our mother earth, it would surely be a great injustice on the part of the younger generation especially the student fraternity to be in utter ignorance of this slow killer as they are the future generations who should live on this earth. Thus taking into considerations these points this project has been taken up not only to know about UV rays but also how it affects the bio diversity of our planet.Here this project deals with the above mentioned points. Also the project aims to give a comprehensive picture on the impending disaster that would take place if we be ignorant on this issue. ACKNOWLEDGEMENT Any people have taken great pains to make this project a reality. First of all I convey my deep thanks to Mrs.@#$% , Dept. of Zoology without whose guidance this project would have become nothing. Also I am deeply indebted to Mrs. ABC , Dept of Botany who too was instrumental in collecting the data required for this project. Last but not the least I deeply acknowledge the help given to me by my classmates whose valuable tips and suggestions helped me bring about such a project. I am deeply indebtedto them for also helping me collect the relevant information from many sources and also providing many diagrams required to emphasise my points. .CONTENTS 1ULTRAVIOLET RAYS 1.1Sources of UV 1.2UV-A, UV-B & UV-C 2EFFECTS OF UV RADIATION ON NATURE AND HUMANS 2.1Damage to marine life 2.2Degradation of polymers, pigments anddyes 2.3HARMFUL EFFECTS ON HUMANS 2.3.1Effects on Eye 2.3.2Effects on Skin 2.3.3Genetic effects 2.3.4Effects on immune system 2.4OZONE DEPLETION AND UV RADIATIONS 2.5VULNERABILITIES DUE TO UV RADIATIONS 1. ULTRAVIOLET RAYS In 1801, the German physicist Johann Wilhelm Ritter, found that there exist invisible rays beyond the violet end of the visible spectrum of the Sun that darken silver chloride even more efficiently than visible light. This spectra region between visible light and X-rays was found to be more chemically active than visible light, and named as the ultraviolet region.Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV.The name means “beyond violet” (from Latinultra, “beyond”), violet being the colour of the shortest wavelengths of visible light. UV light has a shorter wavelength than that of violet lightThe electromagnetic spectrum of ultraviolet light can be subdivided in a number of ways. The draft ISO standard on determining solar radiances (ISO-DIS-21348) Natural sources of UVThe Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands. The Earth’s ozone layer blocks 98.7% of this UV radiation from penetrating through the atmosphere. 98.7% of the ultraviolet radiation that reaches the Earth’s surface is UVA.Other sources: There are also several artificial methods to produce UV rays such as from black light (Wood’s light), Ultraviolet fluorescent lamps, Ultraviolet LEDs, Ultraviolet lasers, synchrotron radiation sources, Argon and deuterium discharge lamps etc…UVA, UVB & UVCAmong the different types of UV, we consider the main subdivisions as UV A, UVB & UV C. UVA(320-400 nm): Ultraviolet light, type A. These are rays of light from the sun which are not visible butcan cause damage to the skin. UVB(280-320 nm) Ultraviolet light, type B. These are rays of light from the sun which are not visible butcan cause damage to the skin.The amount of UV-B light received by a location is strongly dependent on: *.Latitude and elevationof the location: At high-latitude polar regions the sun is always low in the sky. Because the sunlight passes through more atmosphere more of the UV-B is absorbed. For this reason average UV-B exposure at the poles is over a thousand times lower than at the equator. *.Cloud cover: the reduction in UV-B exposure depends the cover’s thickness. *.Proximity to an industrial area:Due to the protection offered by photochemical smog. Industrial processes produce ozone, one of the more irritating components of smog, which absorbs UV-B. This is thought to be one of the main reasons that significant ozone losses in the southern hemisphere have not been mirrored in the northern hemisphere. UVC(100-280 nm): UVC rays are the highest energy, most dangerous type of ultraviolet light. Exposure to it can even lead to death. Little attention has been given to UVC rays in the past since they arefiltered out by the atmosphere. However, their use in equipment such as pondsterilizationunits may pose an exposure risk, if the lamp is switched on outside of its enclosed pond sterilization unit. EFFECTS OF UV RADIATION ON NATURE AS WELL AS HUMANS The effects of UV radiation on earth’s ecosystems are not completely understood. Even isolating the effects of UVA versus UVB is somewhat arbitrary. Studies have shown that increased UV radiation can cause significant damage, particularly to small animals and plants. Phytoplankton, fish eggs, and young plantswith developing leaves are particularly susceptible to damage from over exposureto UV.Solar UV radiation levels are highest during the middle of the day. In total, almost half the daytime total UV radiation is received during the few hours around noontime. The sunlight reaching us consists of only approximately 0.5% UV-B radiation, in terms of radiant energy. Clouds, as well as ozone, have a tremendous affect on UV radiation levels. However, cloudy skies generally do not offer significant protection from UV. Thin or scattered clouds can have minor impacts on UV and even, for a short time, increase UV above what it would be on a blue sky day by further scattering the radiation and increasing the levels that reach the surface.Damage to marine life:The penetration of increased amounts of UV-B light has caused great concern over the health of marine plankton that densely populate the top 2 meters of ocean water. The natural protective-response of most chlorophyll containing cells to increased light-radiationis to produce more light-absorbing pigments but this protective response is not triggered by UV-B light. Another possible response of plankton is to sink deeper into the water but this reduces the amount of visible light they need for photosynthesis, and thereby reduces their growth and reproduction rate. In other words, the amount of food and oxygen produced by plankton could be reduced byUV exposure without killing individual organisms.Degradation of polymers, pigments and dyes:Many polymers used in consumer products are degraded by UV light.