A lens is used as a magnifier to view an ant placed on a piece of paper. the ima

Question

A lens is used as a magnifier to view an ant placed on a piece of paper. the image of the ant is 15cm from the lens and the magnifier factor is 3.
a. how far from the paper (the ant) is the lens?
b. what is the focal length of the lens? is it converging or diverging?
c. is the image virtual or real?
d. suppose you now use new lens whose focal length is 10cm to read a newspaper, but your near point is 30cm. how far should the lens be from the paper?
e. now suppose you use this lens as a part of a camera, and you want to photograph an object which is 50cm to the left of the camera. what is the distance between the lens and the film?
in each case draw a diagram showing how the image is located using atleast two principle rays. one diagram for (a,b,c) for d and for e

Explanation / Answer

I will write out equations as I use them. But these are the lens equations, you should have them. M = -di/do 3 = - -15cm/do do = 15cm/3 = 5 cm. The paper is 5 centimeter away. 1/f = 1/di + 1/do 1/f = 1/-15 + 1/5 1/f= 2/15 f = 7.5 cm Focal is positive, so the lense is converging. I believe the image is virtual. Which is why I used a-15 up above. The image is in front of the magnifying lens. I have never heard the term near point before. I guess that is the desired distance. 1/f = 1/do + 1/di 1/10 = 1/do + 1/-30 2/15 = 1/do do = 7.5 cm Lens and film distance? Is that typedright, because I have no clue.

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