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Which of the following is primarily responsible for warming of the Earth? (i) Solar radiation is immediately absorbed by carbon dioxide, which then releases it as heat. (ii) The atmosphere’s tiny particles absorb incoming solar radiation, which directly heats the Earth. (iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases. (iv) The Earth’s environment is heated only by the solar radiation reflected by the clouds.
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Answer: (iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases
- The surface absorbs sunlight and re-radiates it as infrared; greenhouse gases (CO₂, CH₄, water vapour) trap this outgoing heat.
- This trapped heat, not direct absorption by particles or reflected light, mainly warms the Earth.
Option
Is this how the Earth is warmed?
(i) Solar radiation is immediately absorbed by carbon dioxide, which then releases it as heat
✗ No — CO
2
does not absorb the incoming sunlight; it absorbs the outgoing infrared re-radiated by the surface.
(ii) The atmosphere’s tiny particles absorb incoming solar radiation, which directly heats the Earth
✗ No — particles scatter and absorb a little, but this is not the main warming pathway.
(iii) The Earth’s surface absorbs solar radiation, which is then re-radiated and trapped by greenhouse gases
✓ Yes — surface absorbs sunlight, re-radiates it as infrared, and greenhouse gases trap it. This is the greenhouse effect.
(iv) The Earth’s environment is heated only by the solar radiation reflected by the clouds
✗ No — reflected radiation leaves the system; it does not warm the Earth.
