Worked Examples-Calculation Part 2 - Light

Considered Formula;

$$n = \frac {360}{\theta} - 1$$ $$\qquad \text {Where}~~n \to Number~of~images,\quad \theta \to Angle~between~two~mirrors$$

Example 1

Find the number of images formed by two plane mirrors at 90°

Solution

Data given

Angle between mirrors (θ)= 90°

Number of images (n) = ?

$$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~n = \frac {360}{\theta} - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \frac {360}{90^\circ} - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = 4 - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = 3~images$$

The number of images formed = 3

Example 2

Find the number of images formed by two plane mirrors parallel to each other

Solution

Data given

Angle between mirrors (θ)= 0°

Number of images (n) = ?

$$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~n = \frac {360}{\theta} - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \frac {360}{0^\circ} - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \infty - 1$$ $$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ = \infty$$

The number of images formed = Infinity number of images