Task id16620

A point light source with a luminous intensity I = 100 cd is placed at the focus of a 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 when reflected from the mirror is equal to 25% of the total light energy incident on the mirror (a = 0.25).