Question

10. [15 pts] A 50 m tall tree is located 100 m away from where you are standing. When you put on a pair of glasses, the image of the tree is only 10 m tall and is right-side up. A. Determine the focal length of the lenses in the pair of glasses. Show your work and describe your problem-solving process. f= B. What type of lens is this? For full credit, you must explain your reasoning. O Concave O Convex O Not enough information

Answer 1

magnification = h_i /h_o = v/u = 10/50 = 0.2

v/u = 0.2

v/-100 = 0.2

v = -20

lens formula  

1/v-1/u = 1/f

1/-20 -1/-100 = 1/f

from here f = -25 m answer

B)

it is concave  

explanation

in convex you will get upright image only in case of object is situated between pole and focal length and that case image will be bigger not smaller as in this case so it prove it is a concave lens