Question

If the distance from the focus is 2 mm and the distance from the directrix is 0.5 mm then what is the value of eccentricity?

(a) 0.4

(b) 4

(c) 0.04

(d) 40

The question was posed to me in examination.

This intriguing question originated from Basics of Conic Sections in chapter Curves used in Engineering Practice of Engineering Drawing

Answer 1

The correct option is (b) 4

For explanation: Eccentricity is defined as the ratio of the distance from the focus to the distance from the directrix and it is denoted by e. Therefore, by definition, e = 2 ÷ 0.5 = 4. Hence the conic section is called as hyperbola.