Interferometr Fabry’ego-Perota - Stanowisko Edukacyjne EXP200110
The Fabry-Perot interferometer consists of two parallel semi-reflecting plates (beamsplitters), separated by a distance L (The plate reflection coefficient is greater than 90%). A ray of light entering between the two plates is reflected very many times before it leaves. On each reflection, a portion R of the intensity is reflected and a portion (1 – R) is transmitted. The outgoing rays of light interfere at infinity or in the focal plane of a lens. Multiple interference can be constructive only if all rays are approximately in phase, particularly if there is a large number of rays and thus if R is large. Rays are in phase only for some specific θ angles depending on λ and L.
Zagadnienia edukacyjne (ćwiczenia):
- SPECTROMETRY
The mercury vapour lamp (Hg) contains a spectral doublet made up of two wavelengths very close to one another. Use of a Fabry-Perot interferometer allows these two wavelengths
to be clearly distinguished and their spectral gap to be measured. For this purpose, we shall use an interference filter in order to select only this doublet amongst the spectral range of the mercury lamp. - FABRY PEROT STUDY - FINENESS
To be able to separate the different rings more efficiently, they need
to be as fine as possible. This is equivalent to refining the peaks
in the previous curve, i.e. reduce Δλ with respect to δλ. Thus, a good quality interferometer will exhibit a far lower Δλ than δλ .The greater
the fineness, the finer the rings. To increase fineness, the surfaces making up the cavity can be made highly reflective. Indeed, we can show that fineness increases at the same time as the surface reflection coefficient. Consequently, commercially available Fabry-Pérot interferometers can have finenesses of a few dozens or a few hundreds. In research, this can even attain a few hundred thousands.
This high degree of fineness is a major asset of this type of interferometers with respect to Michelson’s interferometer, which has
a fineness of 2. Thus, the number of oscillations N carried out by light
in the cavity increases at the same time as fineness
SUBJECTS APPROACHED
- Interferences
- Fabry Pérot study
- Wavelength
- Spectrometry
Zalecane Wyposażenie:
- POF020200 Fabry-Pérot Interferometer x1
- POD013210 HeNe laser x1
- POD067040 10x lens x1
- POD002192 Half-moon stand x2
- POD010002 Millimetric metal screen x1
- POD010057 Mercury spectral lamp,
high pressure x1 - POD010572 Filtre interférentiel vert - 546 nm x1
- POD010056 Stand for spectral lamp x1