Why is the telescope objective focal length longer than the eyepiece focal length

Because this can make the distant object very small.

Magnify it at a certain magnification rate to make it have a large opening angle in the image space, so that objects that cannot be seen or distinguished by the naked eye become clear and recognizable.

The first purpose of a telescope is to magnify the opening angles of distant objects, so that the human eye can see details with smaller angular distances. The second function of the telescope is to feed the beam of light collected by the objective lens that is much thicker than the diameter of the pupil (up to 8 mm) into the human eye, allowing the observer to see faint objects that were previously invisible.

In 1608, Hans Lieberch, a Dutch optician, stumbled upon the idea that he could see in the distance with two lenses, and he built the first telescope in human history. Galileo Galilei, a native of Florence, Italy, in 1609.

The 40x double mirror was invented.

Telescope, the first practical telescope to be put into scientific use.

Why does the eyepiece of a telescope have a shorter focal length while the objective lens has a longer focal length.

When using a telescope, in order to make the real image of the distant object through the objective lens as bright as possible, the objective lens should be made larger The larger the objective lens, the more light that can converge, the brighter the image, and the easier it is to observe farther and darker objects The larger the mirror, the longer the focal length of the cluster In order to maximize the angle of view, the distance between the real image formed by the objective lens and the eyepiece should be as close as possible to the focal length of the eyepiece (smaller than the focal length) In order to get more light into the eyepiece (to increase the brightness of the image), The objective lens should be as close to the eyepiece as possible, so the focal length of the eyepiece should be shorter.

Teacher Qi for you.

The objective lens of a microscope is equivalent to a projector.

Between the focal length of the objective lens and the double focal length, an inverted magnified real image is obtained, as if it were outside the other double focal length of the objective. The image obtained by the objective lens falls within the focal length of the eyepiece and is magnified by the eyepiece to produce an upright magnified virtual image.

image relative to the objective lens), and finally obtain a virtual image (relative to the object) of the object inverted and magnified

Due to the limited tube size, the focal length of the objective lens should be shorter to obtain greater magnification.

The image of the objective lens should fall within the focal length of the eyepiece, so the focal length of the eyepiece should be long.

The objective of a telescope is equivalent to a camera, and the object is near the focal point of the objective, resulting in an inverted and zoomed out real image, as if between another focal length and two focal lengths of the objective. The image obtained by the objective lens falls within the focal length of the eyepiece, and is magnified by the eyepiece to obtain an upright magnified virtual image (relative to the image of the objective lens), and finally the virtual image of the object is upside down (relative to the object).This is the Kepler telescope.

The telescope in life is the Galilean telescope.

You can get an upright image.

Because the object distance of the telescope is far greater than the double focal length, the image obtained by the objective lens is near the focal point of the objective lens, and the focal length of the objective lens is larger to facilitate the adjustment of the size of the image, and the focal length of the eyepiece does not need to be too large, because the image position obtained by the objective lens does not change much.

If you have any questions, please feel free to ask.

1. The eyepiece and objective lens are both convex lenses with different focal lengths.

2. The focal length of the convex lens of the objective lens is smaller than that of the convex lens of the eyepiece. The objective lens is equivalent to the lens of the projector, and the object passes through the objective lens into an inverted and magnified real image. The eyepiece is equivalent to an ordinary magnifying glass, and the real image is formed into an upright and magnified virtual image through the eyepiece.

Objects that pass through the microscope to the human eye become inverted and magnified virtual images.

3. The length of the eyepiece and objective lens is opposite to the magnification. The longer the eyepiece lens, the smaller the magnification; The longer the objective lens, the greater the magnification.

4. The overall magnification of the microscope = the magnification of the eyepiece * the magnification of the objective lens.

Why does the eyepiece of a telescope have a shorter focal length while the objective lens has a longer focal length.

Hello, sorry for the wait! The magnification of the telescope is = objective focal length eyepiece focal length, the objective focal length must be longer than the eyepiece to be greater than 1, so that the magnification effect can be known. If the multiple obtained by the reverse is less than that of the swift 1, it is a dusty and shrinking image.

Telescopes have a long focal length because they can see objects more clearly that cannot be seen with the naked eye. The telescope has two functions, one is to magnify the opening angle of distant objects, and the other is to send objects that cannot be seen by the human eye into the human eye so that people can see. Generally, the ratio of the angle of view of the eyepiece to the angle of incidence of the objective lens is used as an indication of the magnification of the telescope.

The reason why the focal length of the telescope objective lens is longer.

The focal length of the objective lens of the telescope is very long because it can magnify the distant object at a small opening angle at a certain magnification, so that it has a large opening angle in the image space, so that the object that cannot be seen or distinguished by the naked eye becomes more clearly distinguishable, that is to say, the object can be seen more clearly.

The first function of a telescope is to magnify the opening angle of distant objects, allowing the human eye to see details with smaller angular distances. The second function of the telescope is to feed the beam of light collected by the objective lens that is much thicker than the diameter of the pupil into the human eye, so that the observer can see faint objects that were previously invisible.

Generally, the ratio of the angle of view of the eyepiece to the angle of incidence of the objective lens is used as the magnification of the telescope, and the ratio of the focal length of the objective lens to the focal length of the eyepiece is usually used to calculate the magnification of the angle of view of the telescope, such as a telescope with a magnification of 10 times, which refers to the ability to magnify the target with a viewing angle of 1 degree to 10 degrees.

The magnification of the telescope is = objective focal length eyepiece focal length, the objective focal length must be longer than the eyepiece to be greater than 1 in order to have a magnification effect.

If the multiple is less than 1 in reverse, the result is a reduced image.

The microscope must first form a magnified real image through the objective lens, and the lens barrel is so short, so a short focal length objective must be used, otherwise there will be no magnification effect; For telescopes, the magnification is the ratio of the focal length of the objective lens to the focal length of the eyepiece, so the focal length of the objective lens must be large.

They also look at different distances, with microscopes looking at things that are extremely close to the objective, while telescopes looking at objects that are infinitely far away or far away.

Can be imaged is can be imaged. That's right. However, for telescopes, which can be imaged, is it called a "telescope"? Obviously, no, you have to zoom in while imaging. My classmates...

And that's the crux of the matter.

If the focal length of the objective lens is smaller than the focal length of the eyepiece, then the image of the telescope is reduced... As for the reason:

First of all, the objective lens will be imaged somewhere in the optical path, what are the characteristics of this imaging? The longer the focal length of the objective, i.e. the smaller the magnification, the larger the image! So the reason why the focal length of the objective lens is longer than the eyepiece is to magnify the image.

Then, the eyepiece magnifies the image through the objective lens and magnified it again!

And then you ask, what does that multiple have to do with it? Since both the objective and the eyepiece are involved in magnification, the magnification is related to both of them. The relationship is this: the longer the focal length of the objective, the shorter the focal length of the eyepiece – the higher the magnification.

However, I don't know what you are asking this question for, if you are making your own telescope, it is very important that the multiplier should not be too high, because of the lens, the lenses and glass used in professional telescopes are not the same as our daily ones, and it is an achromatic lens structure.

If you do it yourself, because the telescope has undergone two-stage magnification (in fact, nearly 10 lenses are used), and the chromatic aberration deformation caused by the front lens will be magnified by the superposition of the back, and it is basically impossible to see it.

So if you are interested, you can understand the principle, but it is recommended not to do it yourself.

The magnification of the telescope = the focal length of the objective eyepiece.

If the focal length of the eyepiece is larger than the focal length of the objective, then it's not a magnified virtual image, it's a reduced virtual image.

In fact, if you turn the telescope upside down, it's not closer, it's farther away, hehe.

I admire the big tirade upstairs.