The Diffraction Grating - Fringe Brightness and Spacing

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SUMMARY

The discussion focuses on the effects of varying wavelength and slit width on diffraction patterns and fringe brightness in light interference experiments. It concludes that a smaller wavelength results in less diffraction and narrower intensity envelopes, while increasing the wavelength leads to wider fringe spacing. Additionally, a larger slit width decreases diffraction, causing the pattern to spread wider. The spacing of fringes is determined by screen distance, wavelength, and slit separation.

PREREQUISITES
  • Understanding of light wavelength and its effects on diffraction
  • Familiarity with single-slit and double-slit diffraction concepts
  • Knowledge of the relationship between slit width and diffraction patterns
  • Basic principles of interference and fringe brightness
NEXT STEPS
  • Research the mathematical principles of single-slit diffraction using the formula for fringe spacing
  • Explore the impact of varying screen distance on diffraction patterns in double-slit experiments
  • Study the effects of different slit separations on interference patterns
  • Learn about the role of wavelength in determining the characteristics of diffraction patterns
USEFUL FOR

Students and educators in physics, optical engineers, and anyone interested in the principles of light interference and diffraction patterns.

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1. Go to http://www.matter.org.uk/schools/Content/Interference/gratingExplored.html .
Q1. What is the effect of varying the Wavelength of the light?


The attempt at a solution. The smaller the wavelength, the lesser the degree of diffraction, as evidenced by the narrower intensity envelope, and vice versa. In addition, the spacing between bright fringes is increased when wavelength becomes bigger

Lingering doubt: When the wavelength changes, is the entire spread of diffraction pattern bigger or smaller? When fringe spacing increases, is it always equal to an increase in overall diffraction pattern spread?



Q2. Set the Wavelength to “600 nm” and the Number of slits to “1” for single-slit diffraction. What is the effect of varying the Slit width?

The attempt at a solution. The bigger the slit width, the smaller the degree of diffractionobserved.The entire diffraction pattern spreads wider when the slit width is smaller.

Lingering doubt: Is it right to say that the fringe spacing increases in addition to the widening of the diffraction pattern when the slit width is smaller?



Q3. Set the Number of slits to “2” for double-slit interference. What is the intensity (brightness of the fringes) envelope dependent on? Fyi, the wavelength remains at 600nm

Attempt at solution.It depends on the slit width only.

Lingering doubt:Does changing the screen distance count? Seems that screen distance changes only the magnification of view. Does, imo NO



Q4. What is the spacing of the fringes dependent on?

Attempt at solution. 3 factors: Screen distance, wavelength of light, slit separation.

Lingering doubt Does changes in fringe spacing in any way determine the diffraction pattern spread? * I know this is a repeated question, but this question has been bugging and confusing me!*
 
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ap_cycles said:
Does changes in fringe spacing in any way determine the diffraction pattern spread? * I know this is a repeated question, but this question has been bugging and confusing me!*
I suspect your real question is something different as it's pretty straightforward to see that as the a wider diffraction pattern is synonymous with increased spacing of the fringes. For example, if you say the central maximum got wider, you mean the dark spots on either side got farther apart, right? So what's really bugging you here?
 
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