Cos ϕ. This light-weight needs to journey farther when compared to the axial light to reach a display, then it strikes the screen at another angle ϕ. The net result would be that the oblique illumination on the monitor is smaller compared to axial illumination by the component cos4 ϕ. https://eduardowumfv.onesmablog.com/5-tips-about-active-remote-sensing-you-can-use-today-69958202