The wavelength of blue light in a synthetic crystal is $$\begin{gathered} 2.91 \\ times10^{-7} \\ textm \end{gathered}$$.

The speed of blue light in this crystal is $$\begin{gathered} 1.38 \\ times10^8 \\ textm/s \end{gathered}$$.

Calculate the frequency of the blue light in the crystal.

Use the equation: $$\begin{gathered} textwavespeed= \\ textfrequency \\ times \\ textwavelength \end{gathered}$$.

Give your answer to 2 significant figures.

A stage performer wears a blue tunic with a white star printed on the front.

What is the colour of the tunic and the star when viewed under red light?

A stage technician claims, 'Under blue light, the star is extremely difficult to see against the tunic.' Explain why.