Class 11 Geography - BIHAR
Solar Radiation Heat Balance and Temperature
This chapter explores how the Earth receives energy from the sun and maintains its thermal equilibrium. You will learn about solar radiation (insolation), factors affecting its distribution, the heat budget mechanism showing how incoming shortwave radiation equals outgoing terrestrial longwave radiation, and the factors controlling atmospheric temperature. For Bihar (BSEB) Class 11 Geography students, this is a core conceptual chapter frequently tested in board exams through short notes, long-answer derivations of the heat budget, and numerical-style questions on temperature lapse rates.
Start Learning FreeKey Concepts
Insolation
Incoming solar radiation received by the earth's surface in the form of short waves, which is the primary source of energy for atmospheric processes.
Albedo
The percentage of solar radiation reflected back by a surface, with fresh snow having a very high albedo and dark forests having a low albedo.
Earth's Heat Budget
The delicate balance between incoming solar radiation (100 units) and outgoing terrestrial radiation, ensuring the earth's average temperature remains relatively constant.
Terrestrial Radiation
Longwave radiation emitted by the heated earth's surface back into the atmosphere, which primarily warms the lower layers of the atmosphere via the greenhouse effect.
Normal Lapse Rate
The rate at which air temperature decreases with an increase in altitude, generally averaging about 6.5 degrees Celsius per 1,000 meters in the troposphere.
Important Formulas
Board Exam Info
In Bihar (BSEB) Class 11 Geography exams, this chapter typically carries around 6 to 8 marks. Expect objective multiple-choice questions on albedo or lapse rate, short answer questions defining insolation and heat budget, and a compulsory or choice-based long answer question detailing the Earth's heat budget with a diagram.
Frequently Asked Questions
Why is terrestrial radiation considered longwave while solar radiation is shortwave?
The sun is extremely hot and emits radiation at very short wavelengths. The earth is much cooler than the sun, so it absorbs that energy and re-emits it at much lower temperatures, resulting in longer wavelengths.
What is the difference between conduction and convection in heating the atmosphere?
Conduction occurs when air touches the warmer earth surface and transfers heat directly through molecular contact. Convection happens when heated air parcels become lighter and rise, transferring heat vertically through the atmosphere.
Why does the earth not overheat despite receiving continuous solar radiation?
Because of the earth's heat budget; the exact amount of energy received from the sun (100 units) is eventually returned back to space through reflection, scattering, and terrestrial longwave radiation, maintaining a thermal equilibrium.
Learn Solar Radiation Heat Balance and Temperature with Your AI Tutor
10 different ways to study this chapter. Free for 3 chapters per day.
Lecture
Key Points
Interactive
Quiz
Flashcards