Reflectors

Reflectors make use of reflective surfaces to direct light where it is needed. They function on the basis of the law of reflection. They may be convergent or divergent.

Most divergent reflectors have a white coating. The efficiency and the way in which light is distributed are primarily determined by the mounting depth of the lamp and dimensions of the reflector. Their shape has only a small influence.

In the case of convergent reflectors, which nowadays are almost exclusively manufactured from polished anodised aluminium, the contours of the reflector play an important role. The following forms are the most common:

 

• Spherical reflectors return the light to the focal point; they are often used as additional reflectors for point-source lamps and spotlights.
• Elliptical reflectors send the rays of light to a second focal point. These reflectors enable a large quantity of light to be directed through small openings, provided small lamps with high luminances are used. The disadvantages are high temperatures at the focal point due to the concentration of the light and heat.
• Parabolic reflectors send the light from a light source out in a parallel beam. The maximum luminous intensity is determined by the luminance of the light source and the diameter of the reflector. Parabolic reflectors are used predominantly in spotlights and narrow angle luminaires.