What do you call an optical filter that blocks the transmission of light outside the designated threshold?

The term used to describe an optical filter that blocks the transmission of light outside a designated threshold is a cutoff filter. This type of filter is designed to allow only a specific range of wavelengths to pass through while completely blocking wavelengths outside of this defined range. For instance, a high-pass cutoff filter will eliminate all light below a certain wavelength threshold, while a low-pass cutoff filter will block all light above a specified wavelength.

Understanding cutoff filters is crucial in applications such as photography, laser applications, and various optical experiments where precise control over light wavelengths is necessary. This control allows for accurate measurements and enhanced image quality by reducing unwanted light interference.