21.2. The Double-Slit Experiment http://www.ck12.org
21.2 The Double-Slit Experiment
Objectives
The student will:
- Understand the Double-Slit Experiment.
- Solve problems involving the Double-slit Experiment.
Vocabulary
- coherent
- monochromatic:Describes a light source in which all the light has exactly the same single wavelength.
- spectroscope:Designed for the purpose of wavelength determination.
- wave interference:A situation in which two waves overlap each other.
Introduction
In geometric optics, we assume light acts like a ray or particle. In other ways, however, it acts like a wave. The
Double-Slit Experiment is a specific case that looks at how light behaves as a wave, following the principle of
superposition.
FIGURE 21.4
Diffraction of a hydrogen lampThe Double-Slit Experiment was first conducted by the British physicist Thomas Young (1773-1829) as convincing
experimental evidence that light was a wave. He demonstrated how superposition led to interference using ripples
in a tank of water. He showed that the same principle also applied to light in the Double-Slit experiment.
Young’s experimental setup is shown inFigure21.6. A singlemonochromaticlight source is to the left, so all the
light has exactly the same single wavelength. The waves are light, shown as ripples in this diagram. The waves