Refraction: Reflection after passing the critical angle

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Discussion Overview

The discussion centers on the concept of total internal reflection, particularly regarding the behavior of light when the angle of incidence exceeds the critical angle. Participants explore the nature of reflection in this context, comparing it to standard reflection in mirrors and discussing the implications for optical devices like total reflection prisms.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the reflection that occurs after passing the critical angle is considered normal reflection, similar to that in mirrors.
  • Another participant cites advantages of total reflection prisms, noting their nearly 100% reflection efficiency compared to ordinary plane mirrors, which are said to have poor reflectivity.
  • Concerns are raised about what happens to light that is not reflected by mirrors, with a participant expressing confusion over the concept of poor reflectivity.
  • Participants discuss the issue of multiple reflections in mirrors, where light can reflect off both the front and back surfaces, leading to absorption losses.
  • Clarification is sought regarding the terminology used, specifically about the front and back surfaces of mirrors and the concept of co-axial rays.

Areas of Agreement / Disagreement

Participants express differing views on the nature of reflection in total internal reflection versus standard reflection in mirrors. There is no consensus on the implications of reflectivity in mirrors or the definition of multiple reflections.

Contextual Notes

Participants have not fully resolved the definitions and implications of terms like "poor reflectivity" and "multiple reflections," which may depend on specific contexts or definitions.

rishch
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If the angle of incidence is greater than the critical angle then it is reflected back into same medium. Is this reflection normal reflection? (as in it obeys all the rules of reflection, like reflection in mirrors) Or is it a bit different?
 
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And also, in my book, under total reflection prisms, they've given the advantages of total reflection prisms as-

The reflection efficiency is nearly 100% as against an ordinary plane mirror whose reflectivity is poor.

There is is no problem of multiple reflections in the case of prisms while this problem spoils the quality of images in mirrors.

How can a plane mirror have poor reflectivity? What happens to the light that is not reflected? I thought mirrors reflected all the light.

And what do they mean by multiple reflection?
 
Total internal reflection follows normal reflection rules.

Mirror absorbs a portion of the light. It also reflects both at the front glass surface and the back surface, that's the multiple-reflection problem the book mentions. Light reflected from the back surface might be reflected back into the mirror again by the front surface, and so on. This will contribute to the absorption losses as well.
 
By front surface you mean the surface of the glass and by back portion you mean the silver reflecting surface on the back right? Oh and what are co axial rays? (Sorry for adding questions every post)
 

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