A light-scattering substance,such as barium sulfate,is used to make the sphere's spherical inner surface and inner wall. The light beam (measurement light) entering the sphere is equally scattered by integrating spheres . The measuring light shines via an aperture in the center of the integrating sphere . The sample is put at this aperture to measure the light passing through the selection and entering the sphere. If possible,the detector should be placed in a gap not directly exposed to measurement light (often at the top or bottom of the integrating sphere). It is possible to achieve uniform radiance and brightness with the use of integrated spheres. Hollow,a spherical shell with highly reflective diffuse interior covering,is called an integrating sphere. There is no difference in the projected solid angle from any point on a sphere to any region on the sphere. This,along with the diffuse coating and many reflections,results in a uniform radiance on and radiance of the sp