Which one of the following is associated with 'Albedo' ?

Question

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Correct — D, reflecting power. Albedo is the fraction of the solar radiation falling on a surface that the surface reflects straight back, expressed either as a ratio from 0 to 1 or as a percentage. A perfect mirror would have an albedo of 1, an ideal black body 0. Fresh clean snow is the highest natural reflector at roughly 80 to 90 per cent, thick cloud is comparable, a sand desert lies in the 25 to 40 per cent range, and forest canopy and open ocean sit below about 10 per cent. Averaged over the whole planet, Earth's albedo is close to 30 per cent — that is, about a third of the sunlight arriving at the top of the atmosphere is returned to space without ever warming anything. Albedo therefore says nothing about how much radiation a body lets through, how much it soaks up, or how much it radiates on its own account; it measures reflection alone.

Why the other options are wrong — (a) Transmissivity describes radiation that passes THROUGH a body — sunlight through window glass or clear water. Albedo counts only what bounces back off the surface; most natural land surfaces transmit almost nothing at all.  (b) The intended trap, because the two are directly linked and easy to invert. For an opaque surface, absorbed radiation equals 1 minus the albedo — so a HIGH albedo means LOW absorption. Fresh snow, with albedo near 0.9, absorbs almost nothing, which is exactly why snowfields stay cold and slow to melt. Calling albedo 'absorbing power' reverses the physics.  (c) Emissivity is the ability of a body to radiate energy at its own temperature — for the Earth that means outgoing long-wave infrared radiation, governed by the Stefan-Boltzmann relation. Albedo belongs to the incoming short-wave half of the heat budget, emissivity to the outgoing long-wave half. Snow illustrates that they are independent: it has a very high albedo for sunlight yet is close to a black body in the infrared.

Concept: Earth's heat budget has an incoming short-wave side and an outgoing long-wave side. On the incoming side, insolation reaching a surface is either reflected or absorbed; albedo is the reflected fraction, and it varies with the nature of the surface, its colour and roughness, and the angle of the sun. On the outgoing side, everything that was absorbed is eventually re-radiated as long-wave infrared, and the greenhouse gases of the atmosphere intercept part of it. Because albedo decides how much energy enters the system in the first place, it is one of the main controls on regional and global temperature.

State PCS 2019 Q95 — Geography PYQ with Answer

State PCS 2019 Q95 — Geography PYQ with Answer