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there are 1000000000000Hz in 1 terahertz
One terahertz is one thousand gigahertz.
Frequencies over 800 Terahertz to about 1600 Terahertz.
The Infrared is roughly from 1 Terahertz to 400 Terahertz, 1012 to 400 1012 .
10 Terahertz to 100 Terahertz (10,000,000,000,000 to 100,000,000,000,000 hertz)