Decrease in which of the following factors leads to an increase in the rate of evaporation?
- A.Ambient temperature
- B.Area of the free surface of the liquid concerned
- C.Wind speed above the surface of the liquid
- D.Humidity
Correct answer
Explanation
The correct answer is D, humidity. Evaporation is the escape of molecules from a liquid surface into the air, and it slows as the air above fills with vapour; when the humidity falls the air can hold more vapour, so the rate of evaporation rises. Option A is wrong because a fall in temperature leaves fewer molecules with enough energy to escape, so evaporation slows rather than quickens. Option B is wrong because a smaller free surface gives fewer molecules the chance to leave, which is why a saucer of water dries faster than the same water in a narrow bottle. Option C is wrong because wind sweeps away the saturated layer of air resting on the surface and keeps the gradient steep, so less wind means slower evaporation. In the heat budget this matters because evaporation carries away latent heat, which is released again when vapour condenses into cloud.
Read the full article: Insolation, Heat Budget and Temperature: Exam Notes
Practice Questions
View allThe incoming solar radiation that reaches the surface of the earth is known as:
- A.Albedo
- B.Insolation
- C.Terrestrial radiation
- D.Isotherm
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The word is a contraction of incoming solar radiation, and it means the short-wave energy from the sun that reaches the earth, measured in India by the India Meteorological Department in units of energy per unit area per unit time.
Read the full explanation →Out of 100 units of insolation received at the top of the atmosphere, how many units are reflected back to space, a share called the albedo of the earth?
- A.14 units
- B.17 units
- C.35 units
- D.51 units
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Of every hundred units of insolation arriving at the top of the atmosphere, about thirty-five are turned back before they can heat the ground, twenty-seven from the tops of clouds, two from snow and ice covered surfaces and the remainder scattered by the atmosphere; this reflected share is the albedo…
Read the full explanation →The normal lapse rate of temperature in the troposphere is about:
- A.1 °C per 1,000 metres
- B.6.5 °C per 1,000 metres
- C.9.8 °C per 1,000 metres
- D.16 °C per 1,000 metres
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This is the normal lapse rate, the average fall of temperature with height in the troposphere, and it is the reason a hill station is cool while the plain at the same latitude is hot.
Read the full explanation →The earth is nearest to the sun, a position called perihelion, on about which date?
- A.3 January
- B.21 March
- C.21 June
- D.4 July
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The orbit of the earth is an ellipse, so the distance from the sun changes through the year; the earth is closest at perihelion about the third of January and farthest at aphelion about the fourth of July, which is option D and the usual distractor in this question.
Read the full explanation →The horizontal movement of air that transfers heat from one place to another is called:
- A.Conduction
- B.Convection
- C.Advection
- D.Radiation
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Advection is the sideways or horizontal transfer of heat by moving air, and in the middle latitudes most of the day to day variation in temperature comes from it; the hot loo that blows over north India in summer and the cold wave that follows a north-westerly wind in winter…
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