Stefan-Boltzmann Law states that the total radiant heat energy emitted from a perfectly black body is proportional to:
A. T^3
B. T
C. T^2
D. T^4
Answer: Option D
Solution (By JKSSB Mock Tests)
The Stefan-Boltzmann law dictates that the total energy radiated per unit surface area of a black body across all wavelengths per unit time (Emissive Power, E) is strictly directly proportional to the fourth power of the black body's thermodynamic (absolute) temperature. E = sigma * T^4, where sigma is the Stefan-Boltzmann constant.
Explanation:
Myopic eye focuses image in front of retina. A diverging (concave) lens spreads light so image falls on retina. Hypermetropia (farsightedness) corrected by convex lens. Bifocals for presbyopia. Cylindrical for astigmatism.
Raindrops fall to the ground with a uniform, constant velocity. This constant velocity is achieved when the gravitational pull is perfectly balanced by:
Explanation:
As a raindrop falls, it accelerates due to gravity. The upward viscous drag force of the air increases with the drop's velocity (Stokes' Law). Eventually, the downward weight of the drop is exactly balanced by the upward buoyant force of the air plus the upward viscous drag force. The net force becomes zero, and it falls with a constant 'terminal velocity'.
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