Atmosphere

Switching from fossil fuels to solar, wind and hydroelectric energy sources.

Step 1: Carbon dioxide (CO₂) is the largest contributor to global warming among greenhouse gases. Step 2: The burning of fossil fuels (coal, oil, natural gas) is the primary source of CO₂ emissions into the atmosphere. Step 3: Switching to renewable energy sources like solar, wind, and hydroelectric power produces electricity without burning fossil fuels, directly reducing CO₂ emissions. Step 4: Option A targets CFCs which deplete ozone but are not the largest contributor to CO₂. Option B reduces nitrous oxide, not CO₂. Option D addresses methane, not CO₂. The question asks specifically about

Mesosphere – because it is difficult to study directly as jets cannot reach it and satellites fly too high.

Step 1: The Mesosphere lies from 50 to 80 km above the Earth's surface. Step 2: This is the layer where most meteors from space burn up due to friction with air molecules, creating the phenomenon we call 'shooting stars'. Step 3: The Mesosphere is nicknamed the 'Ignorosphere' because it is very hard to study – jets and weather balloons cannot fly high enough to reach it, and satellites orbit too high above it. Step 4: The Stratosphere contains the ozone layer and is well-studied. The Ionosphere reflects radio waves and is monitored. The Exosphere still has some gases (hydrogen and helium). Onl

Sun's radiation reaches Earth → Earth absorbs it and radiates heat outward → Greenhouse gases trap some outgoing heat → Earth warms up.

Step 1: Solar radiation (sunlight) passes through the atmosphere and reaches the Earth's surface. Step 2: The Earth absorbs this energy and then radiates it back outward as infrared (heat) radiation. Step 3: Greenhouse gases like CO₂, methane and nitrous oxide in the atmosphere absorb and trap some of this outgoing heat, preventing it from escaping into space. Step 4: This trapped heat warms the Earth — similar to how a greenhouse traps warmth for plants. Step 5: Option A incorrectly says greenhouse gases absorb UV rays (they trap outgoing heat, not incoming UV). Option C is the opposite of wh

CFCs are naturally occurring gases released by wetlands and oceans.

Step 1: The question asks for the INCORRECT statement — so we need to find the wrong fact about CFCs. Step 2: According to the chapter, CFCs are described as 'totally man-made greenhouse gases' — they do NOT occur naturally. Step 3: Wetlands and oceans release methane, not CFCs. Nitrous oxide is released by oceans and soils. CFCs have no natural source. Step 4: Options A, B and D are all correct facts stated in the chapter — CFCs do come from foam in old fridges, are released when fridges are discarded, and are found in aerosol sprays. Step 5: Therefore Option C is the INCORRECT statement beca