Question

Consider a plane wavefront being reflected from the surface of a plane mirror. For this reflection, which of the following statements is not correct?

• A. $A{A}_1$ and $B{B}_1$ are of equal length.
• B. $AB$ and $A_1{B}_1$ are of equal length
• C. $AB$ and $AC$ can never be of same length
• D. All of the above

Answer 1

The correct option is C $AB$ and $AC$ can never be of same length

$A{A}_1=B{B}_1$, since during reflection, there is no change in speed of light, the rays of light will cover equal distance in equal interval of time. Hence option (a) is correct statement.

$AB=A_1{B}_1$ since during reflection, there is no change in width of the wavefront. Hence, option (b) is also correct statement.

$AB$ and $AC$ will be equal when $i={45}^{\circ }.$

Hence, $\left(C\right)$ is the correct answer.

Why this question? To have an in-depth understanding of the phenomenon of reflection of a plane wavefront.