No of images formed by two plane mirrors at 72 degree

Calculate the number of images formed in two plane mirrors, when they are held at the angle of (i) 72° (ii) 36°.

(i) When θ = 72°

Number of image formed = n = `360^circ/theta - 1`

n = `360^circ/72^circ - 1`

n = 5 - 1

n = 4

(ii) When θ = 36°

Number of image formed = n = `360^circ/theta - 1`

n = `360^circ/360^circ - 1`

n = 10 - 1

n = 9

Concept: Images Formed by a Plane Mirrors

Is there an error in this question or solution?

I'm a little confused here since there are varying answers on the internet, and I cannot find any legitimate sources explaining this problem.

According to what I've seen, the formula is simply $$ N = \frac{360^\circ}{A} - 1 $$ However, other sources say that $N$ needs to be an odd number (I do not know why), so when $N$ is even, the answer is actually $N+1$.

If I used the first method, then the answer would be $N=\dfrac{360^\circ}{72^\circ}-1=4$. If I followed the second method, then the answer would be $N+1=5$. (I have actually found some people saying it's 4 and others saying it's 5.)

Could anyone clarify this for me?

An object is placed symmetrically between two plane mirrors inclined at an angle of 72∘, then the total number of images observed will be

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Suggest Corrections