To see your whole body, you don t have to make a mirror the size of yourself

Because it is not convenient to draw pictures here, please prepare a piece of paper and a pen and think while drawing as I said.

The image of an object in a plane mirror is equal in size, equidistant and perpendicular to the plane mirror.

Since people and images are equal in size, they must be as tall. In the diagram, if the person and the image are connected by a line, is it a rectangle?

Since the distance between the person and the image is equal to the plane mirror, is the position of the plane image in the middle of the rectangle?

So now draw a rectangle first. Suppose the left side of the rectangle represents a person, and the right side represents the image of a person in a flat mirror. Then draw a vertical line in the middle of the rectangle to represent the plane mirror.

If we use another line to connect the top of the person's head with the feet of the image, is this line a rectangle diagonal? Does the diagonal line just bisect the plane mirror?

Suppose a person's eyes are on top of his head, and he can see his head and feet at the same time. But is the light he sees at his feet the diagonal we just drawn?

If we remove the lower part of the plane mirror, is that line still there?

Regardless of the distance between the person and the plane mirror, the plane mirror is always in the middle of the rectangle, and the diagonal always bisects the plane mirror.

To sum up, if a person wants to see his whole body image in the plane mirror at the same time, the height of the plane mirror must be half of his height.

Since it is not very convenient to draw and narrate here, the landlord can draw it on paper by himself and understand it more. If you still have any questions, please ask them here.

Because the light from the human foot is reflected by the plane mirror just to the eye on the human head, you can draw a conclusion with the simplest law of light reflection, and you can draw a diagram of the optical path yourself.

Generally, as long as you are half your height, you can see your whole body.

If you connect the eyes of the people on the top of your head and the soles of your feet, you can see your whole body as long as the mirror in the middle leaves the part between the two rays. And this part is exactly half your height.

It's the size of a house!

The mirror should have its own minimum of 1 or 2 large. The median line theorem of the triangle.

It's half the length of your body.

When a person looks in the mirror, he should see his whole body, and the height of the mirror should be at least equal to (half) the height of the person

When we stand in front of a mirror, we are able to see our own image in the mirror because of the reflection of light in the mirror, so how big should the mirror be for a person with a certain height, who wants to see the image of his whole body? When people are farther away from the mirror, they see their own image and become smaller, so can they also see the image of their whole body with a smaller mirror? Let's analyze this problem with the following examples

Example: If a person is meters tall, if the person can see the image of his whole body from the plane mirror, how long is the mirror at least?

First of all, it should be clear that the condition for a person to see the image of an object S from the mirror is that the light emitted by the object S can enter the human eye after being reflected by the plane mirror, as shown in Figure 1, that is, the mirror must be on the line between the image and the eye, or the line between the image and the eye must pass through the mirror The condition that a person can see his whole body is that the upper and lower ends of the portrait and the line of the eye must pass through the mirror

As shown in Figure 2, AB represents the whole body of the person, point C represents the position of the human eye, according to the characteristics of the plane mirror imaging, the image of the person in the mirror A B is made, and A and C, B and C are connected with straight lines respectively From the previous analysis, it can be seen that EF in the figure represents the length that the mirror should have at least

Because a b ef ab and d are the midpoints of aa, and e and f are the midpoints of a c and b c respectively, i.e., ef is the median line of a b c

From the above examples, it can be seen that the condition for a person to see a full-body image of himself in the mirror is that the length of the mirror is at least equal to half of the height When the length of the mirror is equal to half of the height, the person wants to see the image of his whole body, and there is a limit on the height of the mirror, that is, the upper end of the mirror must be the same height as the midpoint of the head and eye line of the portrait (see Figure 3).

When people are farther away from the mirror, the portrait in the mirror becomes farther away from the person, and the image of the person becomes smaller when he sees himself. No matter whether a person is far away from the mirror or close, the conditions for seeing his whole body image are unchanged, and we can visually illustrate this point through Figure 3 After the person moves from AB to A1B1, the connection between the human eye C1 and the upper and lower ends of the portrait A1 and B1 is still over E and F respectively

When people look away from the mirror, they see that the image "becomes smaller" because the angle between the upper and lower ends of the portrait and the line of the human eye (i.e., the viewing angle) becomes smaller, which makes people feel like they have become smaller In fact, because the person itself has not become smaller, and the image of the person is always the same size as the person, so the image of the person is always so big This is the same as the reason we see the car in the distance getting smaller, the car itself has not become smaller, but the perspective of the car to our eyes has become smaller, which makes us feel that it has become smaller

Generally, meters to meters are enough, and the purchase of a mirror should not only consider its functionality, but also consider whether the style and size of the mirror and furniture are reasonable.

According to the specification range of dressing mirrors on the market, the mirror placed upright is enough to see the whole body, and it is difficult to say if it is placed at an angle. In the old fashioned furniture, the "dressing mirror" installed on top of the large wardrobe was a full-length meter. In fact, there is enough rice、。

The height of the mirror is 1 2 people tall, regardless of the distance between the front and back. That is, theoretically, it must be at least half the height of the height, and the upper end of the mirror must be the same height as the top of the portrait's head and the midpoint of the eye line. In fact, if the conditions allow, it is best to use a mirror of equal height, which is more comfortable.

It depends on the position and tilt angle of the mirror, and it is enough to see the whole body when placed upright, and it is difficult to say about the tilted position. In the old fashioned furniture, the "dressing mirror" installed on top of the large wardrobe was a full-length meter. In fact, there is enough rice to see the whole body.

It depends on how far you are from the mirror, and your eyesight.

This should not matter, because the image is the same size as the object, and it has nothing to do with the plane mirror.

4. No matter how you move, you can't see your whole body image.

In order to see your whole body image, the height of the mirror must be at least half the height of the person (i.e., the height of the mirror should not be less than half the height of the person).

The image and object formed by the plane mirror are equal in size, and the vertical distance from the image and the object to the mirror surface is equal. As the person moves, the size of the image does not change.

When the height of the mirror is less than half of the height of the person, no matter how the person moves, he cannot see his or her whole body image.

According to the characteristics of plane near-imaging, the object and image are large, so the size of Xiaohua's image in the mirror will not change;

Because people's eyes see things from near to large and far from small, when people walk in from a distance, the image they see will become larger and larger, and finally they will be equal to their own size, that is, when they stand in front of a mirror

Answer: The size of the image he made in the mirror remains the same, because the image of the plane mirror is large

Xiaohua saw that his image was getting bigger, because the distance between the person and the image became smaller, and the angle of view increased

Solution: As shown in the figure, AD is human, A is the top of the head, D is the foot, B is the eye, FE is the mirror, and FE AD, as FB AD in B, intercept AG 2AB, C is the midpoint of GD, EC AD is in C, EF is the mirror. ag 2ab, bf ag, gd 2gc, ec gd fb bisecting ag, ec bisector gd and ad ef, 2fe ad and ad fe A:

Mirrors at least.