Does the Mirror Equation Apply to Parabolic Mirrors?

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Discussion Overview

The discussion centers on the applicability of the mirror equation, specifically the formula 1/v + 1/u = 1/f, to parabolic mirrors as opposed to spherical mirrors. Participants explore whether the established equations for spherical mirrors can be directly applied to parabolic mirrors, considering the implications of curvature and approximation methods.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Neel questions whether the curved surface mirror formula remains valid for parabolic mirrors, specifically mentioning the equation 1/f = 2/R.
  • Some participants clarify that the equation 1/v + 1/u = 1/f is applicable to spherical mirrors and suggest it can also apply to parabolic mirrors under certain conditions, particularly for rays close to the axis.
  • One participant notes that the mirror equation is derived from the paraxial approximation and implies that the sphericity of the surface may not be a limiting factor for its application to parabolic mirrors.
  • A later post shifts the focus to practical concerns, asking for assistance with aligning parabolic mirrors, indicating a shift from theoretical discussion to practical application.

Areas of Agreement / Disagreement

Participants express varying degrees of agreement regarding the applicability of the mirror equation to parabolic mirrors, with some asserting it is valid under specific conditions while others remain uncertain about the implications of curvature differences. The discussion does not reach a consensus on the matter.

Contextual Notes

The discussion highlights the limitations of the mirror equation's applicability, particularly regarding the conditions under which it holds true, such as the paraxial approximation and the specific characteristics of parabolic versus spherical mirrors.

Who May Find This Useful

This discussion may be of interest to individuals studying optics, particularly those exploring the properties of different types of mirrors and their mathematical descriptions, as well as practitioners seeking practical advice on mirror alignment.

neelakash
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I was wondering whether the curved surface mirror formula (that is usually used to solve convex or concave spherical mirror problems) remains unaltered in case of parabolic mirrors.What might be invalid is the equation 1/f= 2/R...

After all,the equation 1/v + 1/u= 1/f pertains to convex/concave surfaced mirrors...However, I am not sure of it...Can anyone suggest anything?

-Regads,
Neel
 
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neelakash said:
the equation 1/v + 1/u= 1/f pertains to convex/concave surfaced mirrors.
I assume you mean spherical mirrors.
That formula is an approximation - it holds only for rays close to the axis (i.e. not good for very strong lenses/mirrors)
It's equally good for parabolic mirrors with the same proviso.
 
Thank you very much; yes,the mirror equation is a result of paraxial approximation.Although I forgot, probably there was nothing in the proof of the mirror equation that used the sphericity of the surface. It is good that it can also be used for convex or concave paraboloid mirrors (though concave paraboloid mirrors are in more use)...
 
Any body know how to align parabolic mirror?
please help...
 

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