Question

name any two States which have both line of symmetry and rotational symmetry

Answer 1

Smog is a type of severe air pollution. The word "smog" was coined in the early 20th century as a blending of the words smokeand fog to refer to smoky fog, its opacity, and odor. The word was then intended to refer to what was sometimes known as pea soup fog, a familiar and serious problem in Londonfrom the 19th century to the mid-20th century. This kind of visible air pollution is composed of nitrogen oxides, sulphur oxides, ozone, smoke and other particulates. Man-made smog is derived from coal combustion emissions, vehicular emissions, industrial emissions, forest and agricultural fires and photochemical reactions of these emissions.

For other uses, see Smog (disambiguation).

Not to be confused with Smoke.

Smog in New York City as viewed from the World Trade Center in 1988

Quick facts

Smog is often categorized as being either summer smog or winter smog. Summer smog is primarily associated with the photochemical formation of ozone. During the summer season when the temperatures are warmer and there is more sunlight present, photochemical smog is the dominant type of smog formation. During the winter months when the temperatures are colder, and atmospheric inversions are common, there is an increase in coal and other fossil fuel usage to heat homes and buildings. These combustion emissions, together with the lack of pollutant dispersion under inversions, characterize winter smog formation. While photochemical smog is the main smog formation mechanism during summer months, winter smog episodes are still common. Smog formation in general relies on both primary and secondary pollutants. Primary pollutants are emitted directly from a source, such as emissions of sulfur dioxide from coal combustion. Secondary pollutants, such as ozone, are formed when primary pollutants undergo chemical reactions in the atmosphere.