Question

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Item 4

Which statement refers to convection?



Land and ocean absorb and re-emit heat from the sun.



Some of this energy is reflected off Earth's atmosphere.



Warm air rises and takes heat with it; eventually it cools and sinks.



Sunlight travels through space without the aid of fluids or solids.

Answer 1

Answer:

The statement that refers to convection is Warm air rises and takes heat with it; eventually it cools and sinks

Explanation:

There are in general three modes of heat transfer: conduction, convection and radiation.

• In conduction, the heat transfers through contact
• In convection, the heat transfers through density difference
• In radiation, the heat transfers through wave motion

Consider first statement, 'Land and ocean absorb and re-emit heat from the sun'. Radiation is the only mode of heat transfer where there is no requirement for medium. The heat from sun to land and ocean has traveled by radiation. The process of re-emission also occurs in the same way.

Similarly in second statement  the energy reflected of earth's atmosphere traveled by radiation and the last statement where sunlight travels through space without aid of fluids or solids refers to the process of radiation.

In third statement the warm air being less dense rises and takes heat with it; eventually it cools and thereby density increases which causes to sink. Here the movement of air is due to density difference, which concludes that this statement refers to convection