Q128 / 180 · KCET 2010 · Physics

A boat has green light of wavelength $\lambda=500 \mathrm{~nm}$ on the mast. What wavelength would be measured and what colour would be observed for this light as seen by a diver submerged in water by the side of the boat? Given, $\mathrm{n}_{\mathrm{w}}=\frac{4}{3}$.

  • A
    Green of wavelength $376 \mathrm{~nm}$
  • B
    Red of wavelength $665 \mathrm{~nm}$
  • C
    Green of wavelength $500 \mathrm{~nm}$
  • Correct answer
    D
    Blue of wavelength $376 \mathrm{~nm}$

Solution

When light travels from rarer to denser medium its wavelength reduces. Wavelength in water $=\frac{\lambda_{\mathrm{a}}}{\mu_{\mathrm{w}}}$ $$ =\frac{500}{(4 / 3)}=375 \mathrm{~nm} \approx 376 \mathrm{~nm} \text { (Blue colour) } $$

Hence, the correct answer is option: 'D'.

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