critical frequency

[′krid·ə·kəl ′frē·kwən·sē] (electronics) cutoff frequency (electromagnetism) The limiting frequency below which a radio wave will be reflected by an ionospheric layer at vertical incidence at a given time. (geophysics) The minimum frequency of a vertically directed radio wave which will penetrate a particular layer in the ionosphere; for example, all vertical radio waves with frequencies greater than the E-layer critical frequency will pass through the E layer. Also known as penetration frequency.

单词	critical frequency
释义	critical frequency critical frequency [′krid·ə·kəl ′frē·kwən·sē] (electronics) cutoff frequency (electromagnetism) The limiting frequency below which a radio wave will be reflected by an ionospheric layer at vertical incidence at a given time. (geophysics) The minimum frequency of a vertically directed radio wave which will penetrate a particular layer in the ionosphere; for example, all vertical radio waves with frequencies greater than the E-layer critical frequency will pass through the E layer. Also known as penetration frequency. See FCRIT See FCRIT
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