| Radiant energy collection - Patent 4003638 |

| | The **concentrative** capability of the collector, i.e., the ratio of exit aperture transverse dimension d.sub.2 to entrance aperture transverse dimension d.sub.1, is equal to the sine of the half field of view (.theta.) of the **trough**. |

| | The maximum angle of acceptance (critical angle) for **trough** 25 would be equal to the inverse sine of the index of refraction of the medium filling **trough** 21 divided by the index of refraction of the medium filling **trough** 26, i.e. |

| | With respect to **trough** 21, since the exit aperture 23 transverse dimension is equal to 1.5 inches and the desired maximum angle of acceptance is equal to 16.degree., the transverse dimension, d.sub.1, of the entrance aperture 22 would be 5.4 inches and the overall height would be 12 inches. |

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