numericals:
Find the speed of light in diamond whose absolute refractive index is 2.4.

Dear Student,
Please find below the solution to the asked query:

We know that:
refractive index = speed of light in air / speed of light in the medium
speed of light in air = 3×10⁸ m/s
thus,

speed in diamond = speed in air / refractive index =  3×10⁸ / 2.4
speed in diamond =  1.25×10⁸  m/s

Hope this information will clear your doubts about (Light).
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Satyendra Singh