- 31 Mar, 2021
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Lab report
Finish the lab report, no format
For this week’s lab, i recorded the measurements myself. From the video you can gather the data to answer the questions in this report.
See the video in the following link https://mediaspace.msu.edu/media/Wave+interference+experiment+video/1_axdy7ami
In case you cannot see the distances in the video well there are some pictures to help in this link.
Answer the questions from the report and submit it in the d2l dropbox Report 10 submission.
Objectives
(A) To observe light transmitted through a very narrow slits and verify the relationship between the slit width and angles of the transmitted light. (B) To observe light transmitted through two very narrow slits and to verify the relationship between the slit spacing and the angular separation of the transmitted light for the principle peaks.
Part A: Single-Slit Diffraction
Discussion
This week’s and next week’s exercises show that light acts like a wave. Essentially a wave phenomenon known as interference will creating symmetric and rather beautiful patterns. All of matter has a dual nature, acting like both particles and waves. For example, a particle of light (known as a photon) acts like a particle when in collides with an electron. However, that same particle will act like a wave if it is allowed to interfere with other photons, or even with itself.
This dual nature is described by Quantum Mechanics. However, the idea of combined particle and wave nature arose well before the development of Quantum Mechanics in the study of light. Newton argued that light must be particles because it did not appear to diffract and create interference patterns like other waves. Much later, Thomas Young demonstrated that light did diffract. This was one of the first indicators that the strict separation of particles and waves of classical physics was mistaken.
If a plane wave passes through a slit, the slit can be modeled as tiny sources of new waves, all in phase with each other. These sources spread out in all directions. Straight ahead, they all remain in phase and combine for a high intensity. To the sides, the intensity of the wave drops as only some of these wave sources can combine in phase. Eventually, there is no intensity because the sources are all out of phase and the amplitude of the sum is zero.
In the case of light, the relation between the wavelength l of the light, the slit width, and the angle of observation where the intensity of light first becomes zero is:
l = w x sin q (1)
where w is the width of the slit. The geometry is shown in Fig. 1. L is the distance between the slit opening and the center of the screen; s is the distance between the central maximum and the first
minimum. For small angles, sin q » s/L, and Eq. 1 becomes
l = ws /L . (2)
Suppose you measured s and L and the wavelength of the light is known. We could then use Equation (2) to find the slit width by rewriting it as: