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Diffraction - 5

diffraction bsc

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Stella Mary
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23 views10 pages

Diffraction - 5

diffraction bsc

Uploaded by

Stella Mary
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Diffraction

Diffraction grating
• Large number of equidistant narrow rectangular slits of equal width
placed side by side parallel to one another.
• Fraunhofer produced first grating by arranging about 120 narrow slits per
cm using fine wires parallel to one another.
• Later he developed ruled grating over glass by using fine diamond point.
• Two types of grating: Transmission grating and Reflection grating.

If the widths of opaque and transparent portions are respectively ‘a’ and ‘b’,
then, the distance [a + b] is known as “grating constant or grating element”.
Transmission grating – normal incidence

•
Width of principal maxima
•
Grating – certain conditions
•
Transmission grating – oblique incidence
•
Calculate the highest order spectrum for normal incidence which may be seen with monochromatic light of
wavelength 6000 x 10-10 m by means of a diffraction grating having 6 x 105 lines per metre.
Dispersion in grating
•
A diffraction grating containing 5 x 105 lines per metre is used at normal incidence. Calculate the dispersive
power of the grating in the second order spectrum of wavelength region 5 x 10-7 m.

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