When two waves enter the same space at the same time they can interfere in a such a way to cause a larger effect called constructive interference. They can also interfere in such a way to create a smaller effect called destructive interference. Light behaves like a wave and displays these light and dark inference patterns when setup in a clever way.
Check out the Original Double Slit Experiment
Here is another good introduction to the Double Slit Experiment
Big Ideas
Big Idea 6: Waves can transfer energy and momentum from one location to another without the permanent transfer of mass and serve as a mathematical model for the description of other phenomena.
Learning Objectives
BoxSand Learning Objectives
Optics.Interference.LO.BS.1: Understand the two models of light; wave model and particle model
Optics.Interference.LO.BS.2: Be able to understand the difference between the geometry of a sinlge, double, or multi-slit grating
Optics.Interference.LO.BS.3: Be able to understand how a wave and interference pattern for a double-slit are similar but different for multi-slit
Optics.Interference.LO.BS.4: Be able to know when and how to use the small angle approximation
Optics.Interference.LO.BS.5: Be able to understand the condition for far field $r$ vs $d$
Optics.Interference.LO.BS.6: Understand and apply Huygen's principle
Optics.Interference.LO.BS.7: Be able to understand and apply the correct mathematics for single slit vs double slit which can be misleading
Optics.Interference.LO.BS.8: Understand what the fringe order represents
Optics.Interference.LO.BS.9: Be ale to understand the features of a diffraction pattern
Optics.Interference.LO.BS.10: Students should understand the interference and diffraction of waves, so they can apply the principles of interference to coherent sources in order to:
- Describe the conditions under which the waves reaching an observation point from two or more sources will all interfere constructively, or under which the waves from two sources will interfere destructively.
- Determine locations of interference maxima or minima for two sources or determine the frequencies or wavelengths that can lead to constructive or destructive interference at a certain point.
- Relate the amplitude produced by two or more sources that interfere constructively to the amplitude and intensity produced by a single source.
Optics.Interference.LO.BS.11: Students should understand the interference and diffraction of waves, so they can apply the principles of interference and diffraction to waves that pass through a single or double slit or through a diffraction grating, so they can:
- Sketch or identify the intensity pattern that results when monochromatic waves pass through a single slit and fall on a distant screen, and describe how this pattern will change if the slit width or the wavelength of the waves is changed.
- Calculate, for a single-slit pattern, the angles or the positions on a distant screen where the intensity is zero.
- Sketch or identify the intensity pattern that results when monochromatic waves pass through a double slit, and identify which features of the pattern result from single-slit diffraction and which from two-slit interference.
- Calculate, for a two-slit interference pattern, the angles or the positions on a distant screen at which intensity maxima or minima occur.
- Describe or identify the interference pattern formed by a diffraction grating, calculate the location of intensity maxima, and explain qualitatively why a multiple-slit grating is better than a two-slit grating for making accurate determinations of wavelength.
College Board Learning Objectives
Optics.Interference.LO.CB.6.C.1.1: The student is able to make claims and predictions about the net disturbance that occurs when two waves overlap. Examples include standing waves. [SP6.4, 7.2]
Optics.Interference.LO.CB.6.C.1.2: The student is able to construct representations to graphically analyze situations in which two waves overlap over time using the principle of superposition. [SP1.4]
Optics.Interference.LO.CB.6.C.2.1: The student is able to make claims about the diffraction pattern produced when a wave passes through a small opening, and to qualitatively apply the wave model to quantities that describe the generation of a diffraction pattern when a wave passes through an opening whose dimensions are comparable to the wavelength of the wave. [SP 1.4, 6.4, 7.2]
Optics.Interference.LO.CB.6.C.3.1: The student is able to qualitatively apply the wave model to quantities that describe the generation of interference patterns to make predictions about interference patterns that form when waves pass through a set of openings whose spacing and widths are small compared to the wavelength of the waves. [SP 1.4, 6.4]
Optics.Interference.LO.CB.6.C.4.1: The student is able to predict and explain, using representations and models, the ability or inability of waves to transfer energy around corners and behind obstacles in terms of the diffraction property of waves in situations involving various kinds of wave phenomena, including sound and light. [SP 6.4, 7.2]
Enduring Understanding and Essential Knowledge
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Enduring Understanding |
Essential Knowledge |
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Optics.Interference.EU.CB.6.C: Only waves exhibit interference and diffraction. |
Optics.Interference.EK.CB.6.C.1: When two waves cross, they travel through each other; they do not bounce off each other. Where the waves overlap, the resulting displacement can be determined by adding the displacements of the two waves. This is called superposition. Examples include interference resulting from diffraction through slits as well as thin film interference. Optics.Interference.EK.CB.6.C.2: When waves pass through an opening whose dimensions are comparable to the wavelength, a diffraction pattern can be observed. Relevant Equations: $\Delta L = m \lambda$ $d \sin \theta = m \lambda$ Optics.Interference.EK.CB.6.C.3: When waves pass through a set of openings whose spacing is comparable to the wavelength, an interference pattern can be observed. Examples include monochromatic double-slit interference. Optics.Interference.EK.CB.6.C.4: When waves pass by an edge, they can diffract into the “shadow region” behind the edge. Examples include hearing around corners, but not seeing around them, and water waves bending around obstacles. |
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Assumptions
Describe what the assumptions are and why they're important
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History
History
Physics Fun
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