Michelson's rays
Take 15 minutes to prepare this exercise.
Then, if you lack ideas to begin, look at the given clue and start searching for the solution.
A detailed solution is then proposed to you.
If you have more questions, feel free to ask them on the forum.
A Michelson interferometer adjusted in blade air (thickness
) is illuminated by a point source of wavelength
.
The output is placed a convergent lens of focal length
and a screen in its image focal plane.
We reference on the screen bright rings whose radii
are counted from the center :
Bright ring | 1 | 2 | 3 | 4 | 5 |
| 5,02 | 7,11 | 8,7 | 10 | 12 |
Question
What is the path difference
between two beams interfere in a point
on the screen of a distance
from the optical axis ?
Express
as a function of
,
and
.
The path difference is : (see the lesson about the Michelson interferometer)
Question
Deduce data the thickness
of the air blade.
As
, we deduce that :
and
fringes can be exploited : given that the order of interference decreases as further away from the center :
We deduce as :
Question
What is the order of interference at the center ?
is order at the center. It was "almost" a bright fringe at the center.
