Lab 7 - Optical instruments

# Lab 7 - Optical instruments - Physics 8B Lab 7 Optical...

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Physics 8B Lab 7 – Optical Instruments rev 4.0 Lab 7 – Optical Instruments Part I: Multiple Lens Systems The main idea we will use to study how light behaves when passing through multiple optical devices is that we can treat each optical device separately and then combine them. We will apply the rules for ray tracing and use the relationships 1 d o + 1 d i = 1 f and M = " d i d o , for each device one at a time. And then we will combine them using the fact that Image #1 = Object # 2 Image #2 = Object # 3 and M total = M 1 M 2 M 3 ! Etc. Note : The above says that Image #1 serves as Object #2. It does NOT say that the image distance you find for the first device is the number you plug in for the object distance for the second device. You will need to draw pictures and figure out distances accordingly. To see how this works, Set up the optical bench lamp with the letter F at one end of the bench. Place an f = +10 cm lens at a distance of 20 cm from object. Note: You have lenses labeled f = + 10.2 cm at your table. For simplicity we will refer to them as f = +10 cm and you can use the approximation f = +10 cm in any calculations. a) Locate Image #1 with a screen ( Make a note of its position ) i) Record the object and image distances and compute the magnification for the FIRST lens. ii) Is Image #1 bigger, same size, or smaller than Object #1? Inverted or same orientation as Object #1? Is this consistent with the computed magnification M 1 ?

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Physics 8B Lab 7 – Optical Instruments rev 4.0 Now this image will serve as an object for a second lens, i.e. Image #1 = Object #2 Place a second lens f 2 = +10 cm at a distance 30 cm PAST the location of the screen. It is important here and in the remainder of the lab that all lenses are at the same height as the original object. Now remove the screen. b) Locate Image #2 with a screen i) Record the object and image distances and compute the magnification for the SECOND lens. ii) Is Image #2 bigger, same size, or smaller than Object #2? Inverted or same orientation as Object #2? Is this consistent with the computed magnification M 2 ? iii) Is Image #2 bigger, same size, or smaller than Object #1? Inverted or same orientation as Object #1? Is this consistent with the computed magnification M tot = M 1 M 2 ? Notice what Image #2 looks like on the screen. Remove the first lens. Slide the optical bench lamp forward until the letter F is in the same position that Image #1 used to be. Since Image #1 was inverted, rotate the F slide 180 degrees. c) How does the image on the screen compare with the final image on the screen (Image #2) when there were two lenses? d) As far as lens #2 and the screen is concerned, is there any difference between light from a real object and light from an identical image at the same location that had been formed by another lens?
Physics 8B Lab 7 – Optical Instruments rev 4.0 We have seen that (at least for the above example) that we can treat the image of

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Lab 7 - Optical instruments - Physics 8B Lab 7 Optical...

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