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.
Last updated
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.
Practise Optics
665 free Optics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Physics questions like this
Physics is on 7 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
8If the two sound waves produce beats, it is necessary that the two have:
A 16 cm long image of an object is formed by a convex lens on a screen placed normal to its principal axis. On moving the lens towards the screen, without changing the positions of the object and the screen, a 9 cm long image is formed again on the screen. The size of the object is:
A 4 cm high object is located 10 cm from the converging lens, whose focal length is 20 cm. The image so formed will be
A beam of electrons can
A beam of electrons can: