Concave mirrors and horn thermopile senses candle across room.

Concave mirrors and horn thermopile senses candle across room. (Same apparatus as XX ) Concave mirrors are positioned at opposite ends of the lecture table. A candle is positioned at the focal length of one mirror. A horn thermopile is positioned at the focal length of the opposite mirror. The candle flame is thus focused on the elements of the thermopile (which develops about 1 mv. per degree). The signal is amplified and projected onto a screen. Note: The multimeter produces heat and can skew results, so it should be placed outside the mirrors. Leave the amplifier on for the entire demo.