Question

The relation between $\theta$ , $b$ and $D$ is:
(where $\theta$ is the parallax angle, $b$ is the distance between two points of separation, $D$ is the distance of source from any point of observation)

• A. $\theta =\frac{b}{D}$
• B. $\theta =\frac{D}{b}$
• C. $\theta =b\times D$
• D. $\theta =b^2\times D$

Answer 1

Answer: (A)

$\theta =\frac{b}{D}$

From the figure, $\tan \theta =\frac{b}{D}$

For small angle, we have $\tan \theta \sim \theta$

So, we get $\theta =\frac{b}{D}$