Then the view factor F22 is given by

Question

Consider two infinitely long thin concentric tubes of circular cross section as shown in the figure. If D₁ and D₂ are the diameters of the inner and outer tubes respectively, then the view factor F₂₂ is given by                                                 

      (a) $\left ( \frac{D_{2}}{D_{1}} \right )-1$                                                          (b) Zero

      (c) $\left ( \frac{D_{1}}{D_{2}} \right )$                                                                (d) $1-\left ( \frac{D_{1}}{D_{2}} \right )$