O2 refers to two oxygen atoms bonded together, while 2 O refers to two oxygen atoms that are not bonded to each other. They both have two oxygen atoms, but in O2, the oxygen atoms are bonded, while in 2O, the atoms are not.
Answer is A. Because the telescope are use in night
Answer:
Explained
Explanation:
Michelson contrast is used for patterns where the distribution of bright and dark segments is nearly equal.
It is given by:

where I_max = maximum illumination and I_min = minimum illumination
we know that
typically, I_min = 54% of I_max (general standard)
or I_min = 0.54 I_max
putting this value in above equation to get m
this approximately corresponds to m = 0.3 or 30%
hence, 30% recommended as the minimum Michelson contrast