The Diffraction Grating - Fringe Brightness and Spacing

In summary, the effects of varying the wavelength of light and slit width were discussed in relation to single-slit diffraction and double-slit interference. The intensity envelope and spacing of fringes were found to be dependent on the wavelength and slit width. Changes in screen distance were found to only affect the magnification of view. The spacing of fringes was determined to be dependent on screen distance, wavelength of light, and slit separation. There may be some lingering doubt about the relationship between fringe spacing and diffraction pattern spread.
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ap_cycles
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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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FAQ: The Diffraction Grating - Fringe Brightness and Spacing

1. What is a diffraction grating?

A diffraction grating is an optical component that is used to separate and diffract light into its component wavelengths. It consists of a large number of equally spaced parallel lines or grooves, which act as slits for the light to pass through and interfere with each other, resulting in a spectrum of colors.

2. How does a diffraction grating affect the brightness of the fringes?

The diffraction grating's effect on the brightness of the fringes is determined by the number of lines per unit length on the grating. The more lines there are, the brighter the fringes will be. This is because more lines allow for more interference and diffraction of the light, resulting in a more intense pattern of bright fringes.

3. What is the relationship between the spacing of the fringes and the distance between the slits on a diffraction grating?

The spacing of the fringes is directly proportional to the distance between the slits on a diffraction grating. This means that as the distance between the slits increases, the spacing between the fringes also increases. This relationship is known as the grating equation and is given by: d sinθ = mλ, where d is the distance between the slits, θ is the angle of diffraction, m is the order of diffraction, and λ is the wavelength of light.

4. How can we calculate the spacing between the slits on a diffraction grating?

The spacing between the slits on a diffraction grating can be calculated using the grating equation: d = mλ/sinθ, where d is the spacing between the slits, m is the order of diffraction, λ is the wavelength of light, and θ is the angle of diffraction. This equation can be rearranged to solve for any of the variables, depending on the information given.

5. What factors affect the spacing and brightness of the fringes on a diffraction grating?

The spacing and brightness of the fringes on a diffraction grating are affected by several factors, including the distance between the slits, the wavelength of light, the angle of diffraction, and the number of lines on the grating. These factors can be manipulated to produce different patterns and intensities of fringes, making diffraction gratings useful in a variety of applications in science and technology.

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