The SI standard of time is based on: A. the daily rotation of the earth B. the frequency of light emitted by Kr86 C. the yearly revolution of the earth about the sun D. a precision pendulum clock E. none of these Ans: E 2. A nanosecond is: A. 109 s B. 10−9 s C. 10−10 s D. 10−10 s E. 10−12 Ans: B 3. The SI standard of length is based on: A. the distance from the north pole to the equator along a meridian passing through Paris B. wavelength of light emitted by Hg198 C. wavelength of light.
