Alternating violet and red fringes in Diffraction Grating

Therefore, the pattern on the screen is an alternating pattern of different order spectra, with violet and red lights appearing in different orders. This is due to the shorter wavelength of violet light, causing it to be diffracted at a larger angle. In summary, the pattern on the screen formed by white light passing through a diffraction grating is an alternating pattern of violet and red lights in different orders, with violet fringes appearing beyond red fringes due to the shorter wavelength of violet light.
  • #1
huey910
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When white light is passed through the slits in the grate and hits a screen some distance away from the grate, different order spectra appear. My textbook tells me that violet light is always closer to the zeroth order bright fringe than red light because it has a shorter wavelength. However, other sources clearly state that the pattern that appears on the screen is of an alternating pattern of violet and red lights, forming different order spectra. So, why would there be violet fringes beyond red fringes even though their wavelengths remain unchanged?
 
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  • #3
In other words, the 2nd-order violet fringe is beyond the 1st-order red fringe. The statement "violet light is always closer to the zeroth order bright fringe than red light" is only true for a violet and red fringe of the same order; so the 1st-order violet is closer than the 1st-order red, 2nd-order violet is closer than 2nd-order red, etc.
 

1. What is a diffraction grating?

A diffraction grating is a scientific instrument made up of a flat surface with closely spaced parallel lines or grooves. It is used to separate light into its different wavelengths, producing a spectrum of colors.

2. Why do we see alternating violet and red fringes in a diffraction grating?

The alternating violet and red fringes are produced due to the phenomenon of interference. When light passes through the closely spaced parallel lines on a diffraction grating, it diffracts and creates constructive and destructive interference patterns, resulting in the appearance of colored fringes.

3. How does the spacing of the lines on a diffraction grating affect the fringes?

The spacing of the lines on a diffraction grating, also known as the grating constant, determines the angle at which the light is diffracted. The smaller the spacing, the larger the angle of diffraction, resulting in more closely spaced and distinct fringes.

4. Can we observe alternate fringes of other colors besides violet and red?

Yes, the fringes observed in a diffraction grating can range from blue and green to yellow and orange, depending on the spacing of the lines and the wavelength of the incident light.

5. What practical applications do alternating violet and red fringes in diffraction grating have?

Diffraction gratings are used in a variety of applications, including spectrometry, laser technology, and optical communication. The alternating fringes can help in the precise measurement of wavelengths and the characterization of light sources.

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