Which of the following lights travels the fastest in optical fibres?
Correct answer: B. Invisible infra-red.
- A. Visible light.
- B. Invisible infra-red.
- C. Ultra-violet.
- D. Ordinary light.
Explanation
In a material the speed of a wave, light, becomes v=c/n, where n is the refractive index of the material, n differs for each wavelength where it becomes shorter as the wavelength becomes longer since IR has the longest wavelength it disperses the least and is the fastest in optical fibres.
This question appeared on the UHS MDCAT 2008 paper, which you can sit online with every answer explained.
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About Optics
Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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