In a reflecting telescope the objective is a ____.
a. prism
b. mirror
c. lens
d. diffraction grating
e. photographic plate
Question 2
A planetary nebula has a radius of 0.5 pc and is expanding at 20 km/sec. What is the approximate age of this planetary nebula? (1 pc is equal to 3 x 1013 km and 1 year is equal to 3.15 x 107 seconds.)
a. 240 years
b. 790,000 years
c. 96,000 years
d. 960 years
e. 24,000 years