JAMB - Physics (1990 - No. 17)
A light wave of frequency 5 x 10\(^{14}\)Hz moves through water which has a refractive index of \(\frac{4}{3}\). Calculate the wavelength in water if the velocity of light in air is 3 x 10\(^8\)ms\(^{-1}\)
4.5 x 10-7m
6.0 x 10-7m
1.7 x 106m
2.2 x 106m
Explanation
Speed of light in a medium is given by: v = \(\frac{\text{c}}{\text{n}}\)
\(\frac{4}{3}\) = \(\frac{3 \times 10^8}{v}\)
v = 2.25 x 10\(^8\)ms\(^{-1}\)
\(\lambda\) = \(\frac{V}{F}\)
= \(\frac{2.25 \times 10^8}{5 \times 10^{14}}\)
\(\lambda\) = 0.45 x 10\(^{-6}\)m = 4.5×10\(^{−7}\) m
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