Calculating Difference in Speed of Light in Glass: Help Needed!

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SUMMARY

The discussion focuses on calculating the difference in the speed of light in glass for blue and red light, utilizing the refractive indices of 1.643 and 1.618, respectively. The calculated speeds are 1.83 x 10^8 m/s for blue light and 1.85 x 10^8 m/s for red light, resulting in a difference of 2 x 10^6 m/s. Additionally, the discussion addresses finding the time interval for a pulse of white light traveling through a 1 km optical fiber made of this glass, emphasizing the use of the formula d=vt.

PREREQUISITES
  • Understanding of refractive index and its implications on light speed
  • Familiarity with the formula d=vt (distance = velocity x time)
  • Basic knowledge of optical fibers and their properties
  • Concept of light propagation in different media
NEXT STEPS
  • Research the effects of different materials on light speed and refractive index
  • Learn about the principles of optical fiber communication
  • Explore advanced calculations involving light propagation in various media
  • Study the physics of light behavior at interfaces, including total internal reflection
USEFUL FOR

Students studying physics, optical engineers, and anyone interested in the properties of light and its applications in optical technologies.

CathyLou
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Hiya.

I'm really stuck on the following question. I think that I have got part a alright, but I've no idea what to do for part b. Any help would be really appreciated.

The refractive index of glass is 1.643 for blue light, and 1.618 for red.

(a) Calculate the difference in the speed of light in the glass for the two colours.

Okay, for this one I got that if n = C/V, for blue light V = 1.83 x 10^8 and for red light V = 1.85 x 10 ^8. Therefore, the difference is 2 x 10^6 m.s^1.

(b) If a very short pulse of white light is sent in a one end of an optical fibre made of this glass of length 1 km, find the time interval between the arrival at the other end of the red and blue light.

Thank you.

Cathy
 
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Go back to what was probably the very first fourmula you used in physics: d=vt.
 
Chi Meson said:
Go back to what was probably the very first fourmula you used in physics: d=vt.

Oh, yeah! Thanks so much for your help! :smile:

Cathy
 
I also had no idea how to work out the next question and would really appreciate it if someone could please help me out.

A diver working in water has a lamp which is 3 m below the surface. Viewed from above, the lamp produces a circle of light on the surface of the water. What is the diameter of the circle?

Thanks again.

Cathy
 
Last edited:

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