Optics 7 Question 23
23. The phases of the light wave at $c, d, e$ and $f$ are $\varphi _c, \varphi _d, \varphi _e$ and $\varphi _f$ respectively. It is given that $\varphi _c \neq \varphi _f$
$(2007,4 M)$
(a) $\varphi _c$ cannot be equal to $\varphi _d$
(b) $\varphi _d$ can be equal to $\varphi _e$
(c) $\left(\varphi _d-\varphi _f\right)$ is equal to $\left(\varphi _c-\varphi _e\right)$
(d) $\left(\varphi _d-\varphi _c\right)$ is not equal to $\left(\varphi _f-\varphi _e\right)$
Show Answer
Solution:
- All points on a wavefront are at the same phase.
$$ \begin{array}{rlrl} & \therefore & \varphi _d & =\varphi _c \text { and } \varphi _f=\varphi _e \\ \therefore & \varphi _d-\varphi _f & =\varphi _c-\varphi _e \end{array} $$
