A radiation sensor and a small surface of area A1 that emits radiation as a blackbody are...

A radiation sensor and a small surface of area A1 that emits radiation as a blackbody are oriented as shown in the figure. Determine the distance Lat which the sensor is measuring two-thirds of the radiation rate emitted from surface A1 corresponding to the position directly under the sensor at L= 0.

Answer: 0.237 m