Question

The effect of parallax is used to measure:
A. Distances to nearby objects
B. Distances to nearby stars
C. Nearness of atoms in substances
D. The object and image distance in optical experiments

Answer 1

Hint: The method of parallax is based upon the angle subtended by an object with respect to another object in a specific period of time when we know the distance travelled by the object in the period, using the laws of trigonometry we find the distance between the two objects. Here we assume that at least one of the objects performs periodic motion.

Complete answer:
Astronomers estimate the distances of objects in space by using a method which is known as stellar parallax, or trigonometric parallax. Astronomers use an effect which is called parallax to measure distances to nearby stars. Parallax is nothing but the apparent displacement of an object because of a change in the point of view of the observer. As the Earth orbits the sun, a nearby star would appear to move against the background stars which are more distant.

Astronomers would measure a star's position once and then again after 6 months and then calculate the apparent change in position of the star. The method is based on measuring two angles and the included side of a triangle formed by the star, Earth on one side of its orbit and then earth six months later on the other side of its orbit. This method is the parallax method.

Hence option B is the correct answer.

Note:The distance measured by the parallax method is in the unit of astronomical units or light years. The distance measured of nearby objects can be in terms of meters which is the SI unit of distance, or in terms of kilometers and centimeters. The nearness of atoms in substances is of the order of nanometers and angstrom.