Operating light principle

The shadow is formed by light irradiation. Different place has different shadow on earth. Arctic Circle has big shadow, because the sun lights there in oblique angle; the equatorial zone has small shadow, because the sun lights there in perpendicular angle. Carefully observe the shadow of the light, you can find the middle of the shadow is particularly dark, slightly shallow around. Shadow in the middle of the dark part called the umbra, surrounded by gray part called penumbra. These phenomena are closely related to the linear propagation of light.

If put one cylindrical tube on the table, next to it lit a candle, the tube will cast a clear shadow. If you lit two candles next to it, there will be two shadows that do not overlap. Two shadow overlap part did not shoot, is all black, and this is umbra; next to the shadow where only one candle lighted, that is penumbra. If you light three or even four candles, the shadow part will gradually shrink, penumbra will appear a lot of levels. Objects under the light can generate the shadow which composed by umbra and penumbra, also is the principle.

The electric light is illuminated by a curved filament, not just one point. The light from one point is covered by objects, but other light from other points is not all blocked. Obviously, the larger the area of ​​the luminous object, the smaller the umbra. If we lit one circle candle around the above cylindrical tube, then the umbra completely disappeared, penumbra is also light to hard to see.

Scientists made operating light according to the above principles. Lamps which have high luminous intensity are arranged in a round on the lamp panel, synthesis of a large area of ​​light. So that the light can light to the operating table from different angles, ensure that the surgical field has enough brightness, while not producing significant shadow, so named shadowless lamp.