Question

Shown in the figure, are three waves originating from a point source. Points $A,B,C$ lie on trough while points $D,E,F$ lie on crest of the wave. A wavefront emitting from $O$ may pass through,

• A. $A,B,F$
• B. $\text{Either}A,D,E\text{or}B,C,F$
• C. $\text{Either}A,E,C\text{or}B,D,F$
• D. $\text{Either}A,B,C\text{or}D,E,F$

Answer 1

The correct option is D $\text{Either}A,B,C\text{or}D,E,F$


A surface on which, all the particles/points of the medium, are in the same phase, is called a wavefront.

Here, points $A,B$ and $C$ are in the same phase and points $D,E$ and $F$ are also in the same phase.

Hence, a wavefront emitting from $O$ may pass through either from points $A,B,C$ or points $D,E,F$.

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

$\begin{array}{c}\text{Why this question?}\\ \text{Note:- For a point source the wavefront is spherical.}\end{array}$