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 $\left(\varphi _f-\varphi _e\right)$

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Solution:

  1. All points on a wavefront are at the same phase.

$$ \begin{array}{rlrl} & \therefore & \varphi _d & =\varphi _c \text { and } \varphi _f=\varphi _e \\ \therefore & \varphi _d-\varphi _f & =\varphi _c-\varphi _e \end{array} $$



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