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ESE Mechanical 2014 Official Paper - 1

- 0.5
- 1
- 0
- 0.32

Option 1 : 0.5

__Concept:__

Shape Factor is defined as the fraction of radiation energy leaving a surface that reaches another surface, for example, F12 means the fraction of energy leaving the surface 1 reaches surface 2.

Summation Rule: F11 + F12 = 1

Reciprocity theorem: A1 F12 = A2 F21 (A is the surface area)

__Calculation:__

Let us denote the hemishpherical body as body 1, and the flat surafce as body 2

From the summation rule F22 + F21 = 1,

Since no radiation leaving the surface 2 will reach surface 2 again ∴ F22 = 0, F21 = 1

Now from reciprocity theorem,

A1 F12 = A2 F21

2 x π x r2 x F12 = π x r2 x1

**∴ F12 = 0.5**

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