Task id16622

A point light source with luminous intensity I = 100 cd is placed at a distance d = 0.5 m from the spotlight with a radius of curvature of the mirror R = 2 m (Fig.). At a distance l = 5 m from the light source there is a screen E, the plane of which is perpendicular to the optical axis of the spotlight. Find the illumination of the screen at a point lying on the optical axis of the spotlight if the loss of light energy upon reflection from the mirror is equal to 25% of the total light energy incident on the mirror (a = 0.25). Solve the previous problem provided that the light source is at a distance d = 1.5 m from the spotlight.