Shadowless lamps, generally used in the operating room or some night work special lamps,
The principle of which is that the light is refracted to each other, and wash out the shadow.
The electric light is emitted by a curved filament, not limited to one point. The light coming from this one point is blocked by the object, and the light coming from some other point is not necessarily all blocked. Obviously, the larger the area of the luminous object, the smaller the present shadow. If we light a circle of candles around the above tea canisters, this time the shadow completely disappeared, the penumbra is also too faint to see. Scientists based on the above principle made a shadowless lamp for surgery.
Because of the linear propagation of light, when light shines on an opaque object, a shadow is formed behind the object. Shadows vary from place to place and time to time. For example, the shadow of the same person in sunlight is longer in the morning and evening and shorter at noon.?
By observation we can see that the middle part of the shadow of an object under electric light is particularly dark, and the surrounding area is slightly lighter. The middle part of the shadow that is particularly dark we call it the principal shadow, and the surrounding gray part we call it the penumbra. These phenomena are closely related to the principle of linear propagation of light. Through the following experiment you can know the mystery of it.?
We put an opaque cup on a horizontal table, light a candle next to it, and a clear shadow will be cast behind the cup. If two candles are lit next to the cup, two overlapping but not overlapping shadows will be formed; the overlapping part of the two shadows has no light at all, and is therefore completely black, which is the original shadow; next to the original shadow there is only one candle that can be illuminated, which is the half-light, half-dark penumbra. If three or even four or more candles are lit, the penumbra gradually shrinks, and the penumbra appears in many layers and becomes progressively darker.
This is the same reason why an object can produce a shadow consisting of a principal shadow and a penumbra under electric light. An electric lamp is illuminated by a curved filament, and the point of illumination is not confined to a single point. The light from one point gives the object a shadow, while the light from some other point is not necessarily blocked. Obviously, the larger the area of the luminous body, the smaller the present shadow. If we light a circle of candles around the above cup, at that point the penumbra disappears and the penumbra fades so much that it cannot be seen.?
It is for this reason that the overhead light in the operating room consists of several lamps of great luminous intensity arranged in a circle on a disk, synthesizing a large area of light source. This will be able to shine the light from different angles to the operating table, not only to ensure that the surgical field of vision has enough brightness, but also does not produce obvious shadow and affect the operation. So it is named "shadowless lamp".