Question

Parallax method is useful
A. For measuring speed of the light
B. For measuring distances of stars
C. For finding the intensity of light
D. None of the above

Answer 1

Basically, we explain the phenomenon parallax as the apparent displacement of an object because of a change in the observer's point of view. When we see an object along two different lines of sight, displacement or difference in the apparent position of an object occurs. This is known as Parallax. Parallax is measured as angle or semi-angle between those two lines.

Complete answer:
This method called parallax is used by astronomers to measure the distances to nearby stars, they estimate the distance of nearby objects in space using stellar parallax or trigonometric parallax method, as we know that Earth orbits around the Sun and a nearby star will appear to move against the more distant background stars so astronomers measures a star's position once and estimate it again after six months or later and then calculate the relative change in the position, this apparent motion of stars is known as stellar parallax.
In order to see how this method works, just hold your hand out in front of you and close your left eye keeping your right eye open and then look at your hand after that close your right eye keeping your left eye open and then look at your hand, you will notice that your hand is appearing to move against the background.

So, the correct answer is “Option B”.

Note:
Parallax is known as the best way to get distance in astronomy and also astronomers have described parallax as the 'gold standard' for measuring stellar distances because it does not involve physics but depends totally on geometry.