- #1

ab200

- 13

- 3

- Homework Statement
- I want to mount a giant burning lens on the new engineering building and melt down the student commons. The lens will sit 60 m away from the commons (laterally) and tower 40 m above its roof. I can only afford to grind one side of the giant lens to be spherical, so the other side will have to be flat. The glass will have an index of 1.5. What radius of curvature in m is needed to focus the suns rays onto the commons?

- Relevant Equations
- (1/s) + (1/s') = 1/f = (n-1)[(1/R1) - (1/R2)]

(n1/s) + (n2/s') = (n2 - n1)/R

Putting the questionable nature of my professor's problem-writing aside, I found this question pretty confusing. I assumed that 60 m was the focal length, and that R1 was infinity since it is a flat surface. This gives me:

1/60 = (1.5 - 1)[(1/∞) - (1/R2)]

This gave me R2 = 30 m, but that isn't correct.

1/60 = (1.5 - 1)[(1/∞) - (1/R2)]

This gave me R2 = 30 m, but that isn't correct.