The solid angle is defined by a region by the rays of a sphere, and is measured as
Where,
An is projection of incident surface normal to line of propagation.
The plane angle is defined by a region by the rays of a circle, and is measured as\
Where,
L is arc of length and r is radius of circle.
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When the incident surface is a sphere, the projection of surface normal to the line of propagation is the silhouette disk of the sphere which is a circle of the diameter of
If I n denotes the normal intensity and I α represents the intensity at angle α, then
The intensity of normal radiation I n is how much times the emissive power?
A small surface emits diffusively, and measurements indicate that the total intensity associated with emission in the normal direction I n = 6500 W/square m sr. The emitted radiation is intercepted by three surfaces. Mark calculations for intensity associated with emission
Consider a deep-space probe constructed as 1 m diameter polished aluminum sphere. Estimate the equilibrium temperature that the probe reaches if the solar energy received is 300 W/m2. For solar radiation, absorptivity of aluminum is 0.3 and the average emissivity appropriate for aluminum at low temperature is 0.04
The total emissive power of the emitter with area d A and temperature T is given by
A black body of 0.2 m2 area has an effective temperature of 800 K. Calculate the intensity of normal radiations
The energy radiated out decreases with increases in α and becomes zero at an angle of