Band pass filters allow certain frequencies or wavelengths to pass through while blocking others. They can be electronic or optical and are made up of a high pass and low pass filter. They can be built into an IC chip or consist of resistors and capacitors. The gradual effect of the filter can be changed with additional parts. Band pass filters are used in audio and radio equipment, as well as in optics, such as 3D glasses and in astronomy to study distant stars and galaxies.
Devices that accept a signal but only allow certain frequencies within those signals to pass, while blocking all others, are called band pass filters. Some of these filters are electronic and can be used in audio equipment, radio equipment, or other types of circuits. Others are optical and allow only certain wavelengths, or frequencies, of light to pass through.
A band pass filter is made up of two filters put together: a high pass filter, which passes frequencies above a certain threshold, and a low pass filter, which passes frequencies below a certain threshold. A good example of a bandpass filter is an audio filter that only passes frequencies between 20 and 20,000 hertz, as they represent the typical range of human hearing. This filter combines a 20,000 hertz low pass filter with a 20 hertz high pass filter to achieve this.
Band-pass electronic filters can be built into an integrated circuit (IC) chip or can consist of resistors and capacitors or inductors, although capacitors are usually preferred. By changing the resistance values \u200b\u200bof the resistors and the nominal capacity of the capacitors, it is possible to change the effective area of the filter. Many filters use variable resistors to allow the user to easily change their effective area, eliminating the need to rebuild them for minor changes.
One of the major challenges in filter design is that most band pass filters have a gradual effect. Taking the example above, the filter would not eliminate all frequencies below 20 hertz and above 20,000 hertz but, instead, would gradually reduce their size. The gradual effect of the filter can be changed to a more complicated structure, using additional parts.
Bandpass filters are also used in the world of optics, although instead of only letting certain signal frequencies through, they only allow certain wavelengths of light to pass through. An example is a pair of red-blue anaglyph 3D glasses. The red lens is a band pass filter which allows the red light band to pass and the blue lens only allows the blue light band to pass. Astronomers also use band-pass filters, for example, to look only at the ultraviolet or infrared light emitted by distant stars and galaxies to better understand the cosmos.
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