(صورة توضيحية فقط)
The Earth’s stratospheric ozone layer is crucial for life as it absorbs a significant portion of the sun’s harmful الأشعة فوق البنفسجية. It completely blocks the most energetic UVC rays, absorbs about 95% of UVB rays, and allows most of the less harmful جامعة فرجينيا rays to pass through. This filtering effect protects terrestrial life from severe DNA damage.
The ozone layer is a region in the Earth’s stratosphere, roughly 15 to 35 kilometers above the surface, with a high concentration of ozone (O3) molecules. Its protective mechanism is based on a continuous photochemical process known as the ozone-oxygen cycle. When high-energy UVC and UVB radiation strikes an ozone molecule, it splits the molecule into an ordinary oxygen molecule (O2) and a free oxygen atom (O). The formula for this photodissociation is [latex]O_3 + h\nu_{(\lambda < 310nm)} \longrightarrow O_2 + O[/latex]. The free oxygen atom can then recombine with another oxygen molecule to form ozone again, releasing heat in the process: [latex]O_2 + O \longrightarrow O_3[/latex]. This cycle effectively converts harmful UV radiation into thermal energy, warming the stratosphere. The absorption is wavelength-dependent. UVC (100-280 nm) is completely absorbed. UVB (280-315 nm) is strongly but incompletely absorbed, with absorption decreasing as wavelength increases. UVA (315-400 nm) is only weakly absorbed. The discovery of the Antarctic ozone hole in the 1980s revealed that man-made chemicals, particularly chlorofluorocarbons (CFCs), were disrupting this natural cycle by introducing chlorine and bromine atoms that act as المحفزات to destroy ozone, leading to increased UVB radiation at the surface and prompting international action like the Montreal Protocol.
Ozone Layer’s Role in UV Absorption
(إذا كان التاريخ غير معروف أو غير ذي صلة، على سبيل المثال "ميكانيكا الموائع"، يتم توفير تقدير تقريبي لظهوره الملحوظ)
الصور والتنزيلات بالحجم الكامل متاحة فقط، ومجانية تمامًا، للأعضاء المسجلين.
> تسجيل الدخول <
