Optical Center:
Past your near point, because if it were closer, You wouldn’t be able to focus on it. Now, you can measure a lens’ magnifying. Power by comparing the angles at which light. Rays enter your eyes. Every object takes up some amount of your, Field of vision. And, you can express that in Optical Center. Terms of how much that object subtends. An object is to subtend a certain angle. Of your vision based on how close you are, To it, and how big it is.
Optical Center Lens:
If you’re looking up at the moon, and you cover it with your thumb, then your thumb and the moon are both. subtending the same angle to your eye, which we measure in degrees. So if you look at our tiny leaf, it may subtend only, Two degrees of your vision when it’s at your near point. say, 25 centimeters away. But when you look at the leaf through the lens, The virtual image is larger than the actual object. So it subtends six degrees of your vision. To find the magnifying power of the lens Optical Center, You divide the angle subtended by the virtual image. By the angle subtended by your unaided eye. This equation holds true for all magnifiers. Tells you that this particular lens has a magnifying. Power of three.
Converging Lens:
So that’s how a lens can magnify something. That’s right in front of you. But what about an object that’s very far. In the early 17th century, telescopes were. developed in Holland that could magnify, Objects by three or four times. Our friend Galileo heard about this, and in 1609, he built his own telescope that magnified. Objects thirty times! This was a refracting telescope. It consisted of an aim lens on the end closest to the object and an eyepiece at the other end. which magnified the image produced by the aim lens Optical Center. While Galileo used a concave lens for his eyepiece. the standard refracting telescope uses a convex. converging lens for both the aim lens and the eyepiece. Here’s how it works.
Focal Point Optical Center:
The aim lens takes incoming light rays. From a distant source. Since the source is so far away, the incoming, Rays considers parallel. The aim lens then converges the light rays, To form a real, flipped image inside the telescope. This image is very small, but the eyepiece, Acts as a magnifier, forming a large, virtual. Image for the observer to view. Note that the real image is a position, Inside the focal point Optical Center of the eyepiece, maximizing. The size of the virtual image. And the resulting virtual image is still flipped. So any objects viewed through the refracting telescope would be upside down.
Optical Center Telescope:
But that can be correct by using a concave lens for an eyepiece, like Galileo, did. Now, if you want to calculate the magnifying power of the telescope, start with the same equation you used. For the magnifying lens, but with a negative sign, Because the image is a flip. The original subtended angle is the subtended. the angle of the unaided eye – the angle between the center of the lens and the height of the real image. And the subtended angle is the amount that the object subtends. when viewed through the eyepiece – the angle between your eyes. And the rays from the eyepiece Optical Center. Since the angles here are so small, you can assume that the tangent of an angle is roughly equal to the angle itself. And in a ray diagram, you can see the tangent.
