1. The wave model of light is used to explain many of the phenomena discussed in
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Question
1. The wave model of light is used to explain many of the phenomena discussed in this chapter. List at least one of these phenomena and explain it using this model.
2. Explain the difference between diffraction and interference.
3. Explain the condition for constructive interference in a double-slit experiment.
4. The frequency of a light wave in air is 5.3*1014 Hz. Explain how this quantity changes after the light enters a piece of glass
5. State the criteria that will allow you to identify the source of some interference/diffraction patterns
Explanation / Answer
1.One of the phenomena explained by the wave theory is interference.
If light had been constituted of particles rather than being a wave, there would not have been interference and subsequent bright and dark fringes.The bright and dark fringes are respectively the results of constructive and destructive interference of light which proves it to be a wave.
2.Diffraction is the phenomenon by which light bends around corners while interference is the phenomenon by which light waves from two source interact according to phase differences to produce bright and dark fringes.
3.The condition for constructive interference is that the pahse difference of light from two source(phi1 and phi2) should be an integral multiple of 2*pi, i.e.
phi1-phi2=2n*pi, where n is integer
which also implies that the difference in distances(l1 and l2) between the sources and the point of interference should be an integral multiple of wavelrnght,lambda,i.e.
l1-l2=n*(lambda).
4.The frequency of light wave doesn't change when it enters a piece of glass.Instead, its speed and wavelength change(both of them decrease by a factor called the refractive index of glass).
5.The presence of alternate bright and dark bands(fringes) can be a suitable criterion to identify the sources of some interference/diffraction patterns.
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