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Interference and Diffraction EX-5545
Page 1 of 8
Interference and Diffraction of Light
Equipment:
1 1 1 1 1 1 1 1 1 INCLUDED: Basic Optics Track, 1.2 m High Precision Diffraction Slits Basic Optics Diode Laser Aperture Bracket Linear Translator High Sensitivity Light Sensor Rotary Motion Sensor 850 Universal Interface PASCO Capstone OS-8508 OS-8453 OS-8525A OS-8534B OS-8535 PS-2176 PS-2120 UI-5000 UI-5400
Introduction:
The interference maxima for double slits is measured by scanning the laser pattern with a Light Sensor and plotting light intensity versus distance. These measurements are compared to theoretical values. Differences and similarities between interference and diffraction patterns are examined.
Written by Chuck Hunt
Interference and Diffraction EX-5545
Page 2 of 8
Theory
Single Slit Diffraction When diffraction of light occurs as it passes through a slit, the angle to the minima (dark spot) in the diffraction pattern is given by a sin θ = mλ (m=1,2,3, …) Eq. (1)
where "a" is the slit width, θ is the angle from the center of the pattern to a minimum, λ is the wavelength of the light, and m is the order (m = 1 for the first minimum, 2 for the second minimum, ...counting from the center out). In Figure 1, the laser light pattern is shown just below the computer intensity versus position graph. The angle theta is measured from the center of the single slit to the first minimum, so m equals one for the situation shown in the diagram. Notice that the central spot in the interference Figure 1: Single-Slit Diffraction pattern is twice as wide as the other spots since m=0 is not a minimum. Since theta is a very small angle, sin θ ≅ tan θ = xm/L, where xm is the distance from the center of central maximum to the mth minimum on either side of the central maximum and L is the distance from the slit to the screen. Equation 1 now becomes mλ = a sin θ = a tan θ = axm/L Eq. (2)
It is easier to measure the distance (2xm) from the mth
Page 1 of 8
Interference and Diffraction of Light
Equipment:
1 1 1 1 1 1 1 1 1 INCLUDED: Basic Optics Track, 1.2 m High Precision Diffraction Slits Basic Optics Diode Laser Aperture Bracket Linear Translator High Sensitivity Light Sensor Rotary Motion Sensor 850 Universal Interface PASCO Capstone OS-8508 OS-8453 OS-8525A OS-8534B OS-8535 PS-2176 PS-2120 UI-5000 UI-5400
Introduction:
The interference maxima for double slits is measured by scanning the laser pattern with a Light Sensor and plotting light intensity versus distance. These measurements are compared to theoretical values. Differences and similarities between interference and diffraction patterns are examined.
Written by Chuck Hunt
Interference and Diffraction EX-5545
Page 2 of 8
Theory
Single Slit Diffraction When diffraction of light occurs as it passes through a slit, the angle to the minima (dark spot) in the diffraction pattern is given by a sin θ = mλ (m=1,2,3, …) Eq. (1)
where "a" is the slit width, θ is the angle from the center of the pattern to a minimum, λ is the wavelength of the light, and m is the order (m = 1 for the first minimum, 2 for the second minimum, ...counting from the center out). In Figure 1, the laser light pattern is shown just below the computer intensity versus position graph. The angle theta is measured from the center of the single slit to the first minimum, so m equals one for the situation shown in the diagram. Notice that the central spot in the interference Figure 1: Single-Slit Diffraction pattern is twice as wide as the other spots since m=0 is not a minimum. Since theta is a very small angle, sin θ ≅ tan θ = xm/L, where xm is the distance from the center of central maximum to the mth minimum on either side of the central maximum and L is the distance from the slit to the screen. Equation 1 now becomes mλ = a sin θ = a tan θ = axm/L Eq. (2)
It is easier to measure the distance (2xm) from the mth