2.5 Light and Optics 2.5.3 Diffraction and Interference
Dispersion and resolving power of a grating spectroscope
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■■ Rowland grating ■■ Spectrometer ■■ Goniometer
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What you can learn about ■■ Maxwell relationship ■■ Dispersion ■■ Polarisability ■■ Refractive index ■■ Prism
P2210300
Benefits ■■ Understand fundamentals of spectroscopy ■■ Compact setup ■■ Precise and reproducible results
Details
Principle The refractive indices of liquids, crown glass and flint glass are determined as a function of the wave length by refraction of light through the prism at minimum deviation. The resolving power of the glass prisms is determined from the dispersion curves. Tasks 1. To adjust the spectrometer-goniometer. 2. To determine the refractive index of various liquids in a hollow prisms. 3. To determine the refractive index of various glass prism.
4. To determine the wavelengths of the mercury spectral lines. 5. To demonstrate the relationship between refractive index and wavelength (dispersion curve). 6. To calculate the resolving power of the glass prisms from the slope of the dispersion curves. 7. Determination of the grating constant of a Rowland grating based on the diffraction angle (up to the third order) of the high intensity spectral lines of mercury. 8. Determination of the angular dispersion of a grating. 9. Determination of the resolving power required to separate the different Hg-lines. Comparison with theory.
Interference of light
P2220100
What you can learn about ■■ Wavelength ■■ Phase ■■ Fresnel biprism ■■ Fresnel mirror ■■ Virtual light source
Benefits ■■ Observe that light plus light can result in darkness ■■ Understand how to make use of the interference effect ■■ A laser as lightsource allows clear observation
Details
Principle By dividing up the wave-front of a beam of light at the Fresnel mirror and the Fresnel biprism, interference is produced. The wavelength is determined from the interference patterns.
PHYWE SYSTEME GmbH & Co.KG —
Tasks Determination of the wavelength of light by interference 1. with Fresnel mirror, 2. with Fresnel biprism.
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