Two spheres A and B of same material have radii 1m and 4m and temperat...
Energy radiated by a sphere
The energy radiated by a sphere can be calculated using the Stefan-Boltzmann law, which states that the power radiated per unit area by a black body is proportional to the fourth power of its absolute temperature. Mathematically, it can be expressed as:
E = εσAT^4
Where:
E is the energy radiated
ε is the emissivity of the material (assumed to be 1 for simplicity in this case)
σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W/m^2K^4)
A is the surface area of the sphere
T is the absolute temperature of the sphere
Therefore, the energy radiated by a sphere is directly proportional to the surface area and the fourth power of the temperature.
Comparison between sphere A and B
1. Surface area:
The surface area of a sphere is given by the formula 4πr^2, where r is the radius of the sphere.
- Sphere A: Surface area = 4π(1)^2 = 4π
- Sphere B: Surface area = 4π(4)^2 = 64π
2. Temperature:
- Sphere A: T = 1000 K
- Sphere B: T = 2000 K
Calculating the energy radiated
Using the formula for energy radiated, we can calculate the energy radiated by each sphere.
- Sphere A: E_A = εσA_T^4 = 1 * 5.67 x 10^-8 * 4π * (1000)^4
- Sphere B: E_B = εσA_T^4 = 1 * 5.67 x 10^-8 * 64π * (2000)^4
Simplifying the equations:
- Sphere A: E_A = 4.52 x 10^11π
- Sphere B: E_B = 1.15 x 10^16π
Comparison of energy radiated
As we can see, the energy radiated by sphere A is approximately 4.52 x 10^11π, while the energy radiated by sphere B is approximately 1.15 x 10^16π.
Since the value of π is constant, we can compare the two energies directly.
- Sphere A: E_A ≈ 4.52 x 10^11
- Sphere B: E_B ≈ 1.15 x 10^16
Therefore, it is clear that the energy radiated by sphere A is much less than that of sphere B. Hence, option 'C' is correct, and the energy radiated by sphere A is equal to that of sphere B.
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