Total Internal Reflection
2 marks · NormalPrisms are often used in periscopes instead of mirrors. State one advantage of using prisms over mirrors and explain why this is beneficial.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Prisms produce brighter, clearer images than mirrors because total internal reflection in glass does not absorb as much light or lose as much through surface imperfections.
Also accept: Total internal reflection in prisms gives total, lossless reflection.; Prisms give a brighter image because there is less absorption and scattering.
Common mistakes: Just stating 'prisms reflect better' with no reason
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Identifies correct advantage (e.g. brighter, clearer image).
B2 · 1 mark · Explains in terms of total internal reflection in glass being more efficient or involving less light loss than mirrors.
Worked solution
Prisms give a brighter, clearer image because total internal reflection in glass does not lose light, but mirrors may absorb or scatter some light due to surface imperfections.