12) Refraction and Reflection

Question 1

Explain why optical fibres used for communications need to have cladding.

Answer 1

• Keeps signals secure.

- It prevents scratching of the core.

Question 2

State and explain one reason why the middle part of the optical fibre is made as narrow as possible.

Answer 2

• To prevent signal loss from core.

- This would cause signal to get weaker to be less secure.

Question 3

State one application of optical fibres and explain how this has benefited society.

Answer 3

Endoscopes, improve medical diagnosis.

Question 4

State the two conditions necessary for a light ray to undergo total internal reflection at the boundary between two transparent media.

Answer 4

• 𝑛1 > 𝑛2.

- incident angle > critical angle.

Question 5

Describe the structure of a step-index optical fibre outlining the purpose of the core and the cladding.

Answer 5

• Core is transmission medium for em waves to progress by total internal reflection.
• Cladding provides lower refractive index so that total internal reflection takes place
• And offers protection of boundary from scratching which could lead to light leaving the core.