Long Wave-pass Fliter

Long wave pass filters are usually used for wavelength order classification. One side is plated with hard medium long wave pass filter film and the other side is plated with antireflection film, which can cut off sharp light at a specific wavelength, while the other wavelength region has high transmission, so as to achieve the purpose of isolating a wide region of the spectrum

Filter is an optical device used to select the required radiation band. A common feature of filters is that no filter can make the imaging of celestial bodies brighter, because all filters will absorb certain wavelengths, making objects darker.

The filter is made of plastic or glass with special dyes. The red filter can only let the red light pass through, and so on. The transmittance of glass sheet is similar to that of air, and all colored light can pass through, so it is transparent. However, after dyeing with dye, the molecular structure changes, the refractive index also changes, and the passage of some colored light changes. For example, when a white light passes through a blue filter, it emits a blue light, while there are very few green and red light, and most of them are absorbed by the filter.