CBSE Class 10 Science 2019 Outside Delhi Set 1

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Question : 5
Total: 27
The absolute refractive index of Ruby is 1.7. Find the speed of light in Ruby. The speed of light in vacuum is 3×108m∕ s.
Solution:  
We know that,
Refractive index of ruby (µ)
=‌
‌ Speed of light in air (or vacuum) ‌
‌ Speed of light in ruby ‌

So, 1⋅70=‌
3×108
‌ Speed of light in ruby ‌

‌ or Speed of light in ruby ‌=‌‌
3×108
1.7
ms−1

‌=1.76×108ms−1
Thus, speed of light in ruby is 1.76×108ms−1.
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