Question

There are two cavities (Fig. 5.39) with small holes of equal diameters d = 1.0 cm and perfectly reflecting outer surfaces. The distance between the holes is l = 10 cm. A constant temperature T1 = 1700 K is maintained in cavity 1. Calculate the steady-state temperature inside cavity 2.

Instruction. Take into account that a ***** body radiation obeys the cosine emission law.

Answer 1

Taking account of cosine low of emission we write for the energy radiated per second by the ** in cavity # 1 as**

where A is an constant, dΩ is an element of solid angle around some direction defined by the symbol Ω . Integrating over the whole forward hemisphere we get

We find A by equating this to the quantity is stefan- Boltzman constant and d is the diameter of the **.**

where is the solid angle subtended by the ** of 2 at 1. {We are assuming area of **/ (distance)2}