Physics

Problem

The speeds of light in four transparent media P, Q, R and S are

2.25\times10^{8}\,\text{m s}^{-1}

1.80\times10^{8}\,\text{m s}^{-1}

2.00\times10^{8}\,\text{m s}^{-1}

and

2.40\times10^{8}\,\text{m s}^{-1}

respectively. Which sequence gives the correct order of increasing optical density (least to greatest)? a)

Q,\;R,\;P,\;S

S,\;R,\;P,\;Q

S,\;P,\;R,\;Q

S,\;P,\;Q,\;R