33. Geometric Optics
Thin Lens And Lens Maker Equations
Hey, guys, let's do an example. What types of images can be formed by converging lenses? What about diverging lenses? So let's start with converging lenses for converging lenses. We know by convention the focal length is positive. So let's take a look at the thin lens equation and see what types of images we can produce. I'm going toe isolate one over s I. And this becomes one over F minus one over eso. Okay, Bye. Convention. That object distance is always positive for a converging lens that focal length is always positive. So this number could be either positive or negative, depending on if one over F is larger than one over s or if it's smaller. So the image distance is positive. If one over F is larger than one over eso or if eso is larger than not a capital F, it's a lower case F. If that is true, we have a positive image distances. So we have really images. But the image distance can also be negative. The image distance can be negative if one over f is less than one over s not, or if s not is less than one over f then we're gonna have virtual images. Okay, so if your object is placed outside of the focus, if the object distances greater than the focal length, you will always get riel images. But if your object is placed inside of the focus at a distance less than the focal length, you will always get virtual images. Now, what about diverging lenses before even doing any math? What do you guys think are gonna be the images produced by diverging lenses? They should always be virtual, because you can never have converging light from a diverging lens. By convention, the focal length of a diverging lens is negative. So applying the same equation and the same process that image Sorry that object distance is always gonna be positive. But now the focal length is negative, so you have a negative number minus a positive number. That's always going to be negative. So the image distance is always negative, right? That means on Lee. Virtual images can be formed by diverging lenses exactly as we would expect, regardless of what the actual numbers are. Okay, that wraps up this problem. Thanks for watching guys
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