Why is it glaring to be in the dark for a long time when you see the light?

The pupils are big in the dark, small in the bright (controls the amount of light), and you will feel pain when the pupils constrict.

Because you've been in the dark for a long time!

This is because light travels in a straight line in the same homogeneous medium, and when an opaque object is placed in the place where the light source hits, the light emitted from the light source is blocked by the object, forming a dark area. The dark area we call it a shadow. Therefore, where there is light, there must be darkness.

When the opaque body obscures the light source, if the light source is a relatively large luminous body, the shadow produced has two parts, the completely dark part is called the umbra, and the half-light and half-dark part is called the penumbra. The farther an object is from the light source, the longer its umbra will be.

If you look closely at the shadows under the electric light, you will also notice that the shadows are particularly dark in the middle and slightly lighter around them. The darkest part of the shadow in the middle is the umbra, and the darker part around it is the penumbra. The occurrence of these phenomena is closely related to the linear propagation of light.

If you place a cylindrical tea tube on the table and light a candle next to it, the tea tube will cast a clear shadow. If two candles are lit next to the tea tube, two shadows will be formed that overlap but do not coincide. The part where the two shadows overlap is completely black, and this is the umbra; The place where there is only one candle next to the umbra is the half-light and half-dark penumbra.

If you light three or even four candles, the umbra will gradually shrink and the penumbra will appear in many layers. The same is true for objects that can produce shadows composed of umbra and penumbra under electric light.

The lamp is made up of a curved filament that emits light, not just one point. Light from one point obscures the object, and light from other points is not necessarily blocked. Obviously, the larger the area of the luminous object, the smaller the umbra.

If we light a circle of candles around the above-mentioned tea tube, the umbra disappears completely, and the penumbra is too faint to be seen. Shadowless lamps are made according to this principle.

Marx said that everything in the universe is relative, a combination of contradictions. It doesn't matter if you're not poor.

Rich, there is no happiness without pain, there is no failure without success, there is no darkness without light...Everything follows such a metamorphosis relationship. Darkness and light coexist in the world, struggle and develop, and criticize and advance, both of which are indispensable.

There is no darkness, where is the light!