b
(b) The line of sight of the observer remains constant, making an angle of \(45°\) with the normal.

\(\sin \theta = \frac{h}{{\sqrt {{h^2} + {{(2h)}^2}} }}\)=\(\frac{1}{{\sqrt 5 }}\)

\(\mu = \frac{{\sin {{45}^o}}}{{\sin \theta }}\)

\( = \frac{{1/\sqrt 2 }}{{1/\sqrt 5 }} = \sqrt {\left({\frac{5}{2}} \right)} \)