Lecture 27, ACT 1

• The purpose of this ACT is to determine how, if at all, the focal length of a lens changes when it is submersed in water.

  • In air, the focal length of a glass lens (n=1.5) is determined to be fo. When the lens is submersed in water(n=1.3), its focal length ifs measured to be f. What is the relation between fo and f?

(a) f < fo

(b) f = fo

(c) f > fo

• The refraction is determined by the difference in the two indices of refraction

• The smaller the difference,

the less the bend

the longer the focal length

• Think of the case where it is glass “in glass” ! f = infinity !

• Quantitatively, look the lensmaker’s formula

<

Previous slide

Back to first slide

View graphic version