Which of the following statements are correct?
A. Dispersion is the splitting of light into it's constituent colours.
B. The unit for power of a lens is m¯¹.
C. Optical fibres consist of glass fibres coated with a thin layer of material of higher refractive index.
D. Cassegrain telescope has the advantages of a large focal length in a short telescope.
E. Glass is a dispersive medium.
Choose the correct answer from the options given below:

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.