A proposed proximity meter is based on the physical arrangement of Problem 12.14. The sensing area of a meter that is installed on a vehicle, A₂ is irradiated by a stationary warm object, A₁. The sensor's electrical output signal is proportional to its irradiation.

  (a) The object temperature and emissivity are 200°C and ɛ = 0.85, respectively. Determine the distance, L_2.cril, associated with the maximum sensor output signal. Assume the object is a diffuse emitter.

  (b) If the object emits as a nonmetallic material, the total directional emissivity may be approximated as ɛ_θ = ɛ_n, cos θ, where ɛ_n, is the normal emissivity (Problem 12.36). Determine the distance  L_2.cril associated with the maximum sensor output signal.

  (c) Calculate and plot the irradiation of A₂ over the range 0 < L₂ < 10 m.