Write the Word or Phrase That Best Completes Each Statement

Write the word or phrase that best completes each statement or answers the question.
Write a sentence that expresses the relationship in the formula, using the language of variation or proportion.
- $$\mathrm { f } - \text { stop } = \frac { \mathrm { f } } { \mathrm { D } } \text {, where } \mathrm { f } - \text { stop is camera setting with a lens with focal length } \mathrm { f } \text { and diaphragm opening } \mathrm { D }$$