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  2. Heart rate variability - Wikipedia

    en.wikipedia.org/wiki/Heart_rate_variability

    The bands are typically high frequency (HF) from 0.15 to 0.4 Hz, low frequency (LF) from 0.04 to 0.15 Hz, and the very low frequency (VLF) from 0.0033 to 0.04 Hz. [50] HF power reflects stimulation by the parasympathetic nervous system (PNS), whereas LF power reflects stimulation by both the sympathetic nervous system (SNS) and the PNS. [ 50 ]

  3. Skin effect - Wikipedia

    en.wikipedia.org/wiki/Skin_effect

    The AC frequencies used in induction cookers are much higher than standard mains frequency ‒ typically around 25–50 kHz. In electromagnetism , skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases ...

  4. Frequency (statistics) - Wikipedia

    en.wikipedia.org/wiki/Frequency_(statistics)

    A frequency distribution shows a summarized grouping of data divided into mutually exclusive classes and the number of occurrences in a class. It is a way of showing unorganized data notably to show results of an election, income of people for a certain region, sales of a product within a certain period, student loan amounts of graduates, etc.

  5. Intermediate frequency - Wikipedia

    en.wikipedia.org/wiki/Intermediate_frequency

    In communications and electronic engineering, an intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step in transmission or reception. [1] The intermediate frequency is created by mixing the carrier signal with a local oscillator signal in a process called heterodyning , resulting in a signal at the ...

  6. High frequency - Wikipedia

    en.wikipedia.org/wiki/High_frequency

    High frequency (HF) is the ITU designation [1] [2] for the band of radio waves with frequency between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters).

  7. Frequency - Wikipedia

    en.wikipedia.org/wiki/Frequency

    At even lower frequency, the wave is called a microwave, and at still lower frequencies it is called a radio wave. Likewise, an electromagnetic wave with a frequency higher than 8 × 10 14 Hz will also be invisible to the human eye; such waves are called ultraviolet (UV) radiation.

  8. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and ...

  9. Bandwidth (signal processing) - Wikipedia

    en.wikipedia.org/wiki/Bandwidth_(signal_processing)

    The 3 dB bandwidth of an electronic filter or communication channel is the part of the system's frequency response that lies within 3 dB of the response at its peak, which, in the passband filter case, is typically at or near its center frequency, and in the low-pass filter is at or near its cutoff frequency. If the maximum gain is 0 dB, the 3 ...