UPSC Prelims 2010 Q74: Environment & Ecology – Biogeochemical Cycles & Earth Systems
Which one of the following reflects back more sunlight as compared to the other three?
- (a) Sand desert
- (b) Paddy crop land
- (c) Land covered with fresh snow
- (d) Prairie land
Answer: (c) Land covered with fresh snow
Explanation
Which surface reflects the most sunlight
Albedo (reflectivity) varies greatly by surface type, with one option standing out.
| Option | Verdict | Reason |
|---|---|---|
| (a) Sand desert | Incorrect | Sand has a moderate albedo, far lower than fresh snow |
| (b) Paddy crop land | Incorrect | Vegetated cropland has a relatively low albedo, absorbing more sunlight than it reflects |
| (c) Land covered with fresh snow | Correct | Fresh snow has an exceptionally high albedo (often 80-90%+), reflecting most incoming sunlight |
| (d) Prairie land | Incorrect | Grassland/prairie has a moderate-to-low albedo, well below that of fresh snow |
Albedo comparison:
| Surface | Relative albedo |
|---|---|
| Fresh snow | Very high (~80-90%+) |
| Sand desert | Moderate |
| Vegetated land (paddy, prairie) | Low |
Answer: (c) Land covered with fresh snow.
Why each option is right or wrong
- (a) Incorrect. Sand desert's albedo, while moderate, is far below that of fresh snow.
- (b) Incorrect. Paddy cropland, being vegetated, has a relatively low albedo.
- (c) CORRECT. Fresh snow has one of the highest albedo values of any natural surface, reflecting most sunlight.
- (d) Incorrect. Prairie land's albedo is also much lower than fresh snow's.
Key point
FRESH SNOW has the highest albedo (reflectivity) among sand desert, paddy cropland, fresh snow, and prairie land — reflecting most of the sunlight that hits it.
Remember
Among sand desert, paddy cropland, fresh snow, and prairie, fresh snow reflects the MOST sunlight (highest albedo).
Common mistakes
- Underestimating fresh snow's exceptionally high reflectivity compared to other natural surfaces.
- Assuming desert sand, being light-coloured, reflects as much sunlight as snow.
- Not distinguishing vegetated surfaces (lower albedo, more absorption) from reflective surfaces like snow.
Exam tip
Fresh snow = the highest-albedo natural surface, reflecting far more sunlight than sand, cropland, or prairie.
Sources
- NCERT Class XI Geography — Fundamentals of Physical Geography — Solar Radiation, Heat Balance and Temperature
- Savindra Singh — Climatology (Prayag Pustak Bhawan)