Question

What is the coefficient of linear expansion of fused quartz used to make optical flats?

(a) 0.6 x 10^-6/ degree

(b) 0.6 x 10^-5/ degree

(c) 0.6 x 10^-4/ degree

(d) 0.6 x 10^-3 / degree

This question was posed to me at a job interview.

My question is from Optical Flats in division Measurement by Light-Wave Interference of Engineering Metrology

Answer 1

The correct answer is (a) 0.6 x 10^-6/ degree

For explanation: Fused quartz has 0.6 x 10⁻⁶/degree at standard temperature of 20^°C. This low coefficient of linear expansion accounts for its remarkable ability to undergo large, rapid temperature changes without cracking. Borosilicate glass has coefficient of linear expansion not more than 3.6 x 10^-6 /degree.