Category Physics

Most of us don’t think about how our everyday activities might influence the global environment. An example is our use of chlorofluorocarbons or CFCs. These compounds which are useful as propellants in aerosol sprays, refrigerants, and coolants, cleaning agents, insult ants and plastic foam are the main Easters of ozone present in the ozonosphere. Ozonosphere is the general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiative balance of the atmosphere.
It lies roughly between 10 and 50 kilometers, with maximum ozone concentration at about 20 to 25 kilometers. Ozone, O3, a blue gas is unstable allotropic form of oxygen. It is scarce, even in the stratosphere (12 – 50 km from earth’s surface) where it is most concentrated. But each molecule counts. Highly unstable, an ozone molecule readily splits up when hit by ultraviolet radiation. The energy of the life-damaging UV rays is thus converted into harmless heat and never reaches the earth. The breakup leaves a free oxygen atom (O) and an oxygen molecule (O2), the stuff we breathe. The O and O2, in an ongoing cycle, recombine to form new ozone molecules.
The chlorofluorocarbons (trade named freons) released by us are stable and can live up to 100 years.
They are non-toxic and harmless to life. But when they drift slowly upward to reach the stratosphere by convection, they are struck by the high energy short wavelength radiations such as ultraviolet rays and this initiates a ozone clearing process. When a CFC molecule is exposed to strong UV radiation in the stratosphere, it is broken apart.
This release a chlorine atom, which attacks an ozone molecule, pulls away one of the three oxygen atoms and forms a chlorine monoxide molecule thus destroying the ozone molecule. The destructive process continues further.
The oxygen atoms from the new chlorine monoxide molecule are pulled away by free oxygen atoms freeing the chlorine atom to restart the cycle: thus progressively more ozone molecules are decomposed. It has been estimated that one chlorine atom can eat up to 1,00,000 molecules of ozone. A severe depletion in the ozone layer will result in an increase in the case of skin cancer, eye cataract and suppression of the immune system in humans and other species. Food crops sensitive to UV rays could also be affected.
In 1984 a hole in the ozone layer was discovered over Antarctica and more recently a similar hole was discovered which extends over the Arctic, Scandinavia and North America.

ANSWER 1
Cosmic rays are electromagnetic waves of extremely short wavelength. As the word suggests their origin is from outer space or the cosmos. These rays consist of positively charged particles coming from various galaxies outside the solar system and comprise mainly of protons, alpha particles and positive ions of some heavy elements. The sun is a poor source of cosmic rays.
The distant galaxies are the store houses of charged particles. The high electric and magnetic fields present in these galaxies act as natural accelerators of these particles. The high velocities and the charged nature of these particles attribute the wave nature of these particles. Work on the cosmic rays was first stated by Millikan and Anderson during the early part of this century on balloon flights. The intensity of these rays has been found to vary with altitude, latitude and depth under the sea. The primary cosmic rays interact with the molecules of the atmosphere giving rise to secondary particles like electrons positrons (positively charges particles) and mesons. In fact the anti proton was discovered during cosmic ray studies. Luckily, the thick atmosphere around us is a natural blanket protecting us from these rays.
The work of Vikram Sarabhai and Homi Babha on cosmic rays has given us an immense knowledge on the particles that are fundamental constituents of matter and also an insight into the forces that bind them.
Continue reading “What are cosmic rays?”

Terrestrial dust is mostly tiny fragments abraded from things; some of it may be even smaller things aggregating together to form motes of dust. The larger things that turn to dust can be almost anything in the world, from shoes to ships to sealing wax, not to mention cabbages (fragments of dried vegetable matter) and kings (especially if cremated).

Wind-driven dust composed of fragments of stone and clay is so powerful that over the millennia it has cut fantastically shaped canyons and pillars in the badlands of the American west. Drought created the dust Bowl with its penetrating clouds of dry ploughed soil; the fires of ancient plains Indians probably added to the dust in teepees; soot from unburned automobile fuel plagues city apartments.

Dust knows no borders, and dust from volcanic ash lingers in the upper atmosphere to produce brilliant sunsets thousands of miles away from the eruption.

As for why dusting seems worse than futile, one reason is that a dust cloth may simply stir up dust temporarily while the friction simultaneously creates a static electric charge. Charged particles of dust are attracted to surfaces with the opposite charge. An antistatic spray may help by providing a very thin layer of insulation between the opposite charges.