ok. Let’s take a light that came from a star. My eye just seeing a small dot in the sky but with binoculars or a telescope, I can see more information. But the beam of light that came from the star and hit the lens is very small. Where does information come from? Is it already there in the amount of light that comes? Let's take a more powerful telescope and it will give us even more information. But the light that hit the telescope cannot carry so much more information. So where does it come from?russ_watters said:I'm not sure that thinking of it as "information" that is "encoded/decoded" is useful. All lenses do is change the angle at which light hits your eye.
Yes, I understand. but in the moon example, doesn't that mean I'll just see it bigger? How can I see it not only bigger but more detailed?Ibix said:As Russ says, changing the relative positions of the lenses changes the angles at which light enters your eye. So, for example, the angular diameter of the moon as seen from Earth is about half a degree. 8× binoculars would increase that to four degrees. That means you see less through the binocs than you would through an empty tube the same size, but what you do see is larger.
As an aside, there are limits to how much magnificaton is useful even with an ideal optical system. If you keep increasing the magnification there comes a point where you cannot see more detail - you just see blur, no matter how good your optics are. This is the "diffraction limit", and is a kind of limit on information transmitted through a hole of a certain diameter. Very few optical systems are diffraction limited - atmospheric distortion and design trade-offs usually degrade the image long before this becomes relevant.
Does it mean that just changing the angles at which light enters my eye I can change the object size and detail?Ibix said:As Russ says, changing the relative positions of the lenses changes the angles at which light enters your eye. So, for example, the angular diameter of the moon as seen from Earth is about half a degree. 8× binoculars would increase that to four degrees. That means you see less through the binocs than you would through an empty tube the same size, but what you do see is larger.
As an aside, there are limits to how much magnificaton is useful even with an ideal optical system. If you keep increasing the magnification there comes a point where you cannot see more detail - you just see blur, no matter how good your optics are. This is the "diffraction limit", and is a kind of limit on information transmitted through a hole of a certain diameter. Very few optical systems are diffraction limited - atmospheric distortion and design trade-offs usually degrade the image long before this becomes relevant.
If you look at a page in a book too far away, you cannot read the writing. That doesn't mean that the details are not reaching your eye, just that your eye and brain cannot resolve them. With a telescope, the details are magnified so that your eye an brain can process them.grindagrom said:Does it mean that just changing the angles at which light enters my eye I can change the object size and detail?
A star is a bad example because it looks like a point of light either way. A planet, or the moon as in @Ibix's example, is better. The fact that you can see more detail when "zoomed in" is primarily due to the resolution of your eye. The "information" is spread across more rods and cones.grindagrom said:ok. Let’s take a light that came from a star. My eye just seeing a small dot in the sky but with binoculars or a telescope, I can see more information. But the beam of light that came from the star and hit the lens is very small. Where does information come from? Is it already there in the amount of light that comes? Let's take a more powerful telescope and it will give us even more information. But the light that hit the telescope cannot carry so much more information. So where does it come from?
Yes. That's exactly what a telescope or other similar optical system does.grindagrom said:Does it mean that just changing the angles at which light enters my eye I can change the object size and detail?
That's exactly what happens when you try to read a book from 50 feet away and then move to 2 feet away. The book's angular size becomes larger but so do the words on the page. The reason you can't read a book from 50 feet away is because the angular separation between letters (and between points within those letters) is too small. That is, everything is crammed together so close to each other that your eye can't tell the difference between one part of the book and another part close by. You can't 'resolve' the details. Zooming in or moving closer makes the book look bigger, moving the details apart, letting you resolve them.grindagrom said:Yes, I understand. but in the moon example, doesn't that mean I'll just see it bigger? How can I see it not only bigger but more detailed?
Ok. More or less I got it. But some questions remained. The lens is larger than the eye so it collects more light. But there are binoculars with lenses of different sizes but which give the same magnification. This leads to the second issue: the lens system. If it all comes down to lens size and amount of light, then how does the lens system affect that? The amount of light is different (in the case of different lens sizes), but thanks to the lens system, we get the same magnificationDrJohn said:I found this helpful
https://opticsmag.com/how-does-a-magnifying-glass-work/
The eye normally receives parallel beams of light from the target, those directly in front of the eye enter it and the eye's lens brings them to focus on the retina. Other rays not travelling directly at the the eye don't enter it.
As you can see in the diagram on that page referenced above, light that would not enter the eye - the parallel rays that end up hitting the skin above, below, to the left or the right - are bent round (refracted) by the lens and enter the eye, where they then get focused on the retina, producing a bigger image that you'd see without the lens.
Tracing back from the image on the retina to where the object appears to be (it's called a virual image) shows that the object would have to be bigger to form the same sized image on the retina. So it appears bigger.
I admit the optics wasn't my top topic in physics, as it required us to copy diagrams from the board accurately and our lecturer back then simply didn't give us enough time (deliberately, we all suspected, after he got replaced by a human being - he had a nervous breakdown from teaching us) so my notes where usually incomplete, which doesn't help anyone learn. Handouts with good diagrams back then were just not normally given to students. WWW means you can find them and study them to see what they mean.
So study the diagram and you will see what is happening to the light.
In the case of a star, the target star is occupying a tiny TINY area of your field of vision, so forms a tiny image in the eye. With a telescope or binoculars, many more light rays are refracted and give the bigger virual image that you see. The lens on the telescope or binoculars are much bigger than your eye's lens.
And all the same about the star. I think it's interesting. A star that is billions of light years away emits rays of light. These rays diverge in all directions. How much of this light will reach the Earth? But even such a small Hubble telescope can give us a huge amount of information about this star. The diameter of its mirror is only 2.4 meters. In my opinion, only individual photons of this star should reach it.russ_watters said:A star is a bad example because it looks like a point of light either way. A planet, or the moon as in @Ibix's example, is better. The fact that you can see more detail when "zoomed in" is primarily due to the resolution of your eye. The "information" is spread across more rods and cones.
Use the inverse square lawgrindagrom said:How much of this light will reach the Earth?
If you actually wanted an answer you could actually calculate the "number of photons" involved, rather than idly speculating..grindagrom said:In my opinion, only individual photons of this star should reach it.
No, it isn't. The star is zero angular size, still covering only one rod/cone even through a telescope.grindagrom said:And all the same about the star.
Hubble can't see individual stars from billions of light years away, only galaxies. But yes, it would capture single digit photons per second at most from a star that far away. We can calculate that...A star that is billions of light years away emits rays of light. These rays diverge in all directions. How much of this light will reach the Earth? But even such a small Hubble telescope can give us a huge amount of information about this star. The diameter of its mirror is only 2.4 meters. In my opinion, only individual photons of this star should reach it.
Lens size determines how much light it gathers. The focal length of the lens determines its magnification. I can take my telescope and block out the outer 50% of the aperture and it will still have the same magnification.grindagrom said:The lens is larger than the eye so it collects more light. But there are binoculars with lenses of different sizes but which give the same magnification. This leads to the second issue: the lens system. If it all comes down to lens size and amount of light, then how does the lens system affect that? The amount of light is different (in the case of different lens sizes), but thanks to the lens system, we get the same magnification
Stars are bright. VERY bright. They are very nearly the brightest things in the universe after all. Only beaten by stellar and cosmological events like supernovas and quasars.grindagrom said:A star that is billions of light years away emits rays of light. These rays diverge in all directions. How much of this light will reach the Earth? But even such a small Hubble telescope can give us a huge amount of information about this star. The diameter of its mirror is only 2.4 meters. In my opinion, only individual photons of this star should reach it.
To clarify for the OP, Hubble and other large telescopes can't resolve individual stars except for very large stars that are very close, such as Betelgeuse.russ_watters said:Hubble can't see individual stars from billions of light years away, only galaxies.
Spyglasses and binoculars have a zoom feature to allow the user to see objects that are far away in greater detail. This is especially useful for activities such as bird watching, stargazing, or surveillance.
The zoom feature on spyglasses and binoculars works by using a combination of lenses and prisms to magnify the image. By adjusting the position of the lenses, the user can change the level of magnification and bring distant objects into focus.
Optical zoom refers to the physical magnification of the image through the use of lenses, while digital zoom uses software to enlarge the image. Optical zoom provides a higher quality image as it does not rely on digital manipulation.
Yes, spyglasses and binoculars can zoom in on objects that are too far away to see with the naked eye. The level of magnification depends on the power of the lenses and can vary between different models of spyglasses or binoculars.
Yes, there is a limit to how much spyglasses or binoculars can zoom in. This limit is determined by the power of the lenses and the quality of the image. Going beyond this limit can result in a blurry or distorted image.