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The Ozone Layer.

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Introduction

The Ozone Layer Introduction Since the mid 1980's scientists have been aware of the continuing depletion occurring in the ozone layer. First discovered over the South Pole, these holes are thought to be the cause of excessive use of chlorofluorocarbons (CFC's, found in aerosols and refrigerators) and emissions from the petrochemical industry. Ozone (O?) itself is a highly reactive and unstable form of oxygen found in the stratosphere, but, while poisonous to humans if inhaled, it is also our natural defence against UV radiation. As people become more aware of this worsening problem and the effects of UV on the skin the demand for more effective chemical sunscreens has intensified - enter the chemists. Aim The aim of my investigation is to try different sun blocks of the same brand (differing factors) to test their UV blocking properties and attempt to identify the active ingredients used. I'll also test some household products for their UV blocking effectiveness. My results should then help me answer the question, "what makes a good sunscreen?". Research Ultraviolet Light... (1) UV radiation reaches the earth's surface in two types: UVa - wavelength between 320 - 400nm UVb - wavelengths between 280 - 320nm UVc is wavelength 200 - 280nm, however, this doesn't reach the earth's surface as the stratosphere absorbs it. ...read more.

Middle

Safety Precautions Wear UV protective glasses Avoid prolonged direct exposure to UV If people coming into contact with sunscreens have any nut allergies then take extra care with handling etc Avoid naked flames when working with paraffin If anything is accidentally swallowed then seek medical attention Method Apparatus... ? Sunscreens, factor 4, 8 and 12 ? Aqueous Cream ? Paraffin mix (1/2 liquid paraffin, 1/2 white soft paraffin) ? Microscope Slides (all 1.07mm thick) ? Cover Slips ? Retort Stands ? UV Lamp ? UV Detector ? Stop Clock ? UV Protective Sunglasses ? Metre Rule ? Micrometer Method: Measurements will be made regarding UV intensity in Wm. The actual experiment will take place in a dark room (help avoid interference from background UV), with the UV source clamped vertically in a retort stand and aligned with the UV detector (clamped in another stand). In between the source and detector will be another stand, holding the slide, test material and coverslip so that the detector is as close as possible to the slide and is directly behind the 'test area' (bit covered in sunscreen). ...read more.

Conclusion

0.07 40 0.65 0.33 0.21 0.14 0.90 0.07 60 0.62 0.33 0.21 0.14 0.10 0.07 80 0.63 0.33 0.21 0.14 0.09 0.07 100 0.63 0.32 0.21 0.14 0.09 0.07 120 0.63 0.32 0.19 0.14 0.09 0.07 140 0.63 0.32 0.19 0.14 0.09 0.07 160 0.63 0.32 0.20 0.13 0.09 0.07 180 0.64 0.33 0.20 0.14 0.09 0.07 200 0.63 0.33 0.20 0.14 0.09 0.08 220 0.63 0.33 0.20 0.14 0.10 0.07 240 0.63 0.31 0.20 0.14 0.10 0.07 260 0.63 0.31 0.21 0.14 0.10 0.07 280 0.63 0.31 0.21 0.14 0.10 0.07 300 0.61 0.31 0.21 0.14 0.10 0.07 Average 0.63 0.32 0.20 0.14 0.10 0.07 Paraffin 50/50 Mix Distance of UV Source/cm Time/sec 5 10 15 20 25 30 0 0.80 0.40 0.32 0.17 0.11 0.07 20 0.70 0.40 0.32 0.17 0.11 0.07 40 0.70 0.39 0.31 0.17 0.12 0.07 60 0.70 0.39 0.31 0.17 0.11 0.07 80 0.70 0.38 0.31 0.17 0.11 0.07 100 0.70 0.39 0.30 0.17 0.11 0.07 120 0.70 0.39 0.30 0.17 0.11 0.07 140 0.70 0.40 0.30 0.17 0.10 0.07 160 0.70 0.39 0.30 0.17 0.11 0.07 180 0.70 0.39 0.30 0.17 0.11 0.07 200 0.70 0.39 0.30 0.17 0.11 0.07 220 0.70 0.39 0.30 0.17 0.11 0.07 ...read more.

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