Black paper is commonly used for measuring visible light because it absorbs a wide range of visible wavelengths and minimizes reflections. The purpose of using black paper or black surfaces is to reduce the influence of scattered or reflected light, ensuring that the measured light is primarily coming from the source of interest.
Black paper appears black because it absorbs most of the visible light incident upon it. When light strikes the surface of the paper, the pigments or materials within the paper absorb the light across a broad spectrum of visible wavelengths, preventing it from being reflected back or transmitted through the paper. As a result, the black paper minimizes the presence of unwanted reflections or scattered light in the measurement setup, allowing for more accurate measurements of the light source.
However, it's important to note that black paper is not effective in measuring infrared or ultraviolet (UV) light. This is because the absorption properties of black paper are primarily tailored to the visible spectrum, and it may not be designed to absorb light outside of that range.
For measuring infrared or UV light, different materials or coatings are used that are specifically designed to absorb or attenuate those particular wavelengths. These materials are often selected based on their known absorption properties in the respective wavelength ranges. For instance, certain types of glass or filters can be used to block or attenuate UV light, while specialized materials or detectors are employed for detecting and measuring infrared radiation.
Therefore, when working with different regions of the electromagnetic spectrum like infrared or ultraviolet, specific materials or coatings suitable for those wavelengths are employed to ensure accurate measurements and control unwanted light interactions.