A monochromatic light wave is travelling in vacuum along the direction $\frac{1}{\sqrt{2}}(\hat{i}+\hat{j})$. The wavefront of the light wave is represented by:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → x + y = constant
The direction of propagation of light wave is -
$\vec K=\frac{1}{\sqrt{2}}(\hat i+\hat j)$
The equation of a plane is -
$\vec r.\vec n$ = constant
where,
$\vec r = x\hat i+y\hat j+z\hat k$
$\vec n = \hat k=\frac{1}{\sqrt{2}}(\hat i+\hat j)$
$∴\frac{1}{\sqrt{2}}x+\frac{1}{\sqrt{2}}y$ = constant
⇒ x + y = constant