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University of Wisconsin - Milwaukee

# A stamp collector uses a lens with 7.5-cm focal length as a simple magnifier. The virtual image is produced at the normal near point (25 cm). (a) How far from the lens should the stamp be placed? (b) What is the expected angular magnification?

## a. 5.77 \mathrm{cm}b. 4.33

#### Topics

Electromagnetic Waves

Wave Optics

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### Video Transcript

so we have the focal length off a magnifier is seven point point five centimeter. Also, it is given that the virtual images produced by this magnifier at the normal near point, that means the image distance is going to be a negative 25 centimeter. So for part A to find up. Victor says P. We just used the lens equation, which is water or F, because whatever p plus one of acute and from here P is going to be Q times F over Q minus F, and we know the value of Q, which is negative. 25 negative, 25 times 7.5 over negative, 25 minus 7.5. So this is going to give us 5.77 centimeter as the object distance. So to go to part B, when the image of the object is formed at the near point, then the magnification is maximums. So in this case, the magnification is going to be a max, and that's going to be cool to one plus 25 centimeter over for the length of the magnifier magnifier. So this is going to give us one plus 25 over 7.5, and this will give us 4.33 which is the angler magnification

University of Wisconsin - Milwaukee

#### Topics

Electromagnetic Waves

Wave Optics