The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature T K is given by (where σ is Stefan's constant)

Question

Dr. Abubacker · Accepted Answer

[Solution from source] The star emits σT⁴ × 4πr² in total. At distance R this spreads over a sphere of area 4πR², so energy per unit area per second = σT⁴·4πr²/(4πR²) = σr²T⁴/R². Keeping the 4π in the numerator forgets to divide by the full sphere area. Answer (2).

Q. The total radiant energy per unit area, normal to the direction of incidence, received at a distance R from the centre of a star of radius r, whose outer surface radiates as a black body at a temperature T K is given by (where σ is Stefan's constant)

Explanation

Reviewed by Dr. Abubacker

Want to attempt the full paper?