Question

The significance of greenhouse gases in earth’s atmosphere is
A. They maintain a warm temperature on earth by absorbing short-wavelength radiations.
B. They do not allow earth’s atmosphere to drop very low by spreading heat energy of long wavelength radiations.
C. They reflect the Sun's heat back to the atmosphere.
D. Both (1) and (2).

Answer 1

Hint: Greenhouse gases are the gases that absorb and emit radiant energy within the thermal range. There are about 5 main greenhouse gases, namely, carbon-dioxide, water vapour, methane, ozone and sulphur dioxide

Complete solution:
Greenhouse effect is the natural process of warming the earth’s surface. When the sunlight reaches the earth surface, some of the sunlight reflects back, some is absorbed and some are re-radiated by these greenhouse gases. This causes the atmosphere to get warm. This warming up maintains the survival of the organism on the earth’s surface. They do not allow the temperature on the earth to drop very low as they spread long wavelength radiations.

The highest contributor of green-house gases is carbon-dioxide. It is produced mostly by burning fossil fuels. Methane is produced when vegetation is burnt in absence of oxygen. Nitrous oxide is released mainly by burning of fossil fuels and by chemical fertilizers. These gases are responsible for causing greenhouse effects.

Presence of excess greenhouse gases in the atmosphere causes global warming. They trap most of the sunlight instead of escaping back into space. This raises the earth temperature by causing social and economic effects. The life of different organisms living in different habitats gets affected due to which species become more prone to extinction.
Correct answer is option B.

Note: Greenhouse gases are responsible for maintaining the temperature of the atmosphere. Excess release of these gases is harmful as they cause global warming. Global warming raises the earth’s temperature causing harmful effects on the environment.