A brief explanation about the frequency

1. FREQUENCY (HERTZ)

2. FREQUENCY DEFINITION
Frequency is the number of occurrences of repeating event per
unit time. (t)
HERTZ
The SI unit of frequency is the herts (Hz) named after the german
physicist Heinrich Herts.
One herts means that an event repeats once per second. The previous
name for this unit was cycles per second (cps). The SI unit for period is
the second

3. The period is the reciprocal of the frequency, and vice versa. Period is
expressed in units of time.
PERIOD

4. FREQUENCY AND WAVELENGTH
The wavelength and frequency of light are
closely related. The higher frequency has
the shorter the wavelength and the lower
frequency has the longer the wavelength
WAVELENGTH
The wavelength is the length of one
complete wave cycle. Wavelength is
expressed in units of length.

5. ELECTROMAGNETIC SPECTRUM FREQUENCIES

6. FREQUENCY MEASUREMENT
By counting f=c/λ
By stroboscope – An older method of measuring the frequency of
rotating or vibrating objects
By frequency counter – Higher frequencies are usually measured with a
frequency counter, it is an modern method.
Heterodyne method – Above the range of frequency counters,
frequencies of electromagnetic signals are often measured indirectly by
means of heterodyning (frequency conversion)

7. AUDIO FREQUENCY
Sound propagates as mechanical vibration waves of pressure and
displacement, in air or other substances.
Frequency is the property of sound that most determines pitch
The audible frequency range for human is about 20Hz to 20000Hz
The speed of sound is approximately independent of frequency, so the
wavelength of the sound waves is approximately inversely proportional to
frequency

8. FREQUENCY BANDS
Band Description Frequency Wavelength
VLF Very Low 3 – 30 kHz 100 – 10 km
LF Low 30 – 300 kHz 10 – 1 km
MF Medium 300 – 3000 kHz 1 km – 100 m
HF High 3 – 30 MHz 100 – 10 m
VHF Very High 30 – 300 MHz 10 – 1 m
UHF Ultra High 300 – 3000 MHz 1 m - 10 cm
SHF Super High 3 – 30 GHz 10 - 1 cm
EHF Extremely High 30 – 300 GHz 1 cm – 1 mm
Higher frequency means shorter wavelength.
Shorter frequency means longer wavelength.

9. FREQUENCY BAND AND APPLICATION
AM RADIO - 535 KHZ TO 1.7 MHZ
SHORT WAVE RADIO - 5.9 MHZ TO 26.1 MHZ
GPS - 1.227 GHZ TO 1.575 GHZ
WIFI - 2.4 GHZ AND 5 GHZ
BLUETOOTH - 2.45 GHZ
RADIO ASTRONOMY OBSERVATION - 30GHZ TO 1 THZ
CELLULAR NETWORKS - 900MHZ TO 1800 MHZ

10. THANK YOU
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SANTHOSHHSOURCE : INTERNET