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Anonymous users2024-01-24First, the role of the door mirror.
If you look out through the door mirror from the inside, you can see all the scenes within the range of about 120 degrees from the outside of the door, but you can't see anything inside through the door mirror If you install this mirror on the door of a public house or private apartment, it can play a certain role in the anti-theft and security of the family
Second, the optical principle of door mirror imaging.
The door mirror is composed of two lenses When we look out from the inside of the door, the objective lens L1 is a concave lens, and the eyepiece L2 is a convex lens (see Figure 1 for the optical path) The focal length of the objective lens L1 is extremely short, and it AB the outdoor person or object AB into a very small upright virtual image A B, this image just falls in the first focus of the eyepiece L2, L2 plays the role of a magnifying glass, and finally obtains a more magnified upright virtual image A B, which is just around the bright distance of the human eye, and can see clearly for the situation outside the door
Why, then, when you look in from the outside of the door (upside down) through this mirror, you can't see anything?
When viewed backwards (see Fig. 2 for the optical path), L1 becomes an eyepiece, L2 becomes an objective lens, and the indoor scene AB, the refracted beam after passing through the converging lens L2 should have generated an inverted real image A B, but it falls on the divergent lens L1 before it is imaged, due to.
The focal length of L1 is extremely short, and the final upright virtual image A B is very close to the eyepiece L1, only 2 3cm, and because the aperture of the door lens is very small, people outside have to get close to the eyepiece.
L1 inspection, in this way, the distance between the human eye and like A B, is only 2 3cm, this distance is much smaller than the near point of the normal human eye, therefore, for the outdoor peeper, of course, everything indoors is "blind" (the near point is the minimum distance that the human eye can see clearly The near point distance increases with age, the near point of normal young people is about 10cm, but the near point of normal people is about 40cm when they are 50 years old).
First, the role of the door mirror.
If you look out through the door mirror from the inside, you can see all the scenes within the range of about 120 degrees from the outside of the door, but you can't see anything inside through the door mirror If you install this mirror on the door of a public house or private apartment, it can play a certain role in the anti-theft and security of the family >>>More
Concave mirrors.
Because, the role of the cat's eye is to use a smaller hole to see a larger range, the flat mirror does not have this effect, and the convex lens will produce a magnifying effect, the image is large, the range is also large, where you can't see a larger range, only the concave mirror has a narrowing effect, the image is small, and the range of seeing is also large. >>>More
This is a combination lens.
Have you noticed that this cat's eye can only see clearly from the inside out, and you can't see things clearly from the outside to the inside? The reason for this is that this is a combination lens, a device that combines a convex lens and a concave lens. >>>More
The principle of reducing the image of a convex lens in the refraction of light at 2x the focal length is applied.
Concave lenses. Concave lenses can only be upright. Reduced virtual image. >>>More