Why we draw the normal?

1. Jul 4, 2006

Please explain with another simple example

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2. Jul 4, 2006

DaveC426913

If you didn't, how would you measure i or r?

What would you do in the case of a curved surface?

3. Jul 5, 2006

Staff: Mentor

The normal, which is perpendicular to the plane forming the interface between media (e.g. solid and gas), is simply a reference. The maximum transmission of light comes when the beam (photons) is parallel with the normal.

4. Jul 5, 2006

garyljc

The normal is indeed a reference =) We need the normal (as what Astronuc said, perpendicular to the plane) to measure indexes .

5. Jul 5, 2006

andrevdh

When we develop the maths to describe the physics we try to make the maths as simple as possible. So the theory dictated that if we use the normal to the interface between the two media the maths will be much easier and natural to the real situation. You can also see that, using the normal as the reference for the angles, when the incident angle is zero the refraction angle will also be zero, which makes the most sense does'nt it? Refraction problems were also initially solved with graphical techniques in which case the normal were used in the diagrams (seee history of Willebrord van Roijen Snell - also called Snellius).