Answer: [tex]65.9^{\circ}[/tex]
Explanation:
Given
Intensity must be reduced by a factor of 6
Intensity is given by [tex]I=I_o\cos ^2\theta\\[/tex]
Substitute [tex]I[/tex] by [tex]\frac{I_o}{6}[/tex]
[tex]\Rightarrow \dfrac{I_o}{6}=I_o\cos ^2\theta\\\\\Rightarrow \cos^2\theta =\dfrac{1}{6}\\\\\Rightarrow \cos \theta=\dfrac{1}{\sqrt{6}}\\\\\Rightarrow \theta=65.9^{\circ}[/tex]
So, the disk must be rotated by an angle of [tex]65.9^{\circ}[/tex] .
