What is parallax method? Derive expression for measuring the distance between earth and sun and also diameter of sun?
Answers
Answer:
Parallax is the effect whereby the position or direction of an object appears to differ when viewed from different positions.
Parallax is defined as the apparent shift of a body with respect to another, with the shift of eye.
The distance between planets and stars from the Earth can’t be measured directly with a metre scale. Hence indirect method called the parallax method is used.
Explanation:
To measure the distance d of sun (S1) from earth by parallax method, we observe it from two diametrically opposite positions on the earth. A and B on the earth, separated by distance b.
Measure the angle between two directions along which the sun is viewed at these two points.
Angle= θ = θ1+ θ2
Distance d<<b
b = AB = 2R= 2 * radius of earth
sin θ= θ = b/d
therefore, d= b/ θ
θ should be measured in radians.
Diameter of Sun:
The angular diameter of sun is angle subtended by two diametrically opposite ends of sun at a point on the Earth.
Let, D diameter of Sun and d be distance between sun from the earth. D<<d
Arc length AB=D=d deta θ