A hollow enclosure is formed between two infinitely concentric cylinders of radii 1 m and 2 m respectively. Radiative heat exchange takes place between the inner surface of the larger cylinder (surface −2) and the outer surface of the smaller cylinder (surface−1) the radiating surfaces are diffuse and the medium in the enclosure is non-participating. The fraction of the thermal radiation leaving the larger surface and striking itself is A. 0.25 B. 0.5 C. 0.75 D. 1
