When the light from two lamps falls on a screen, no interference pattern can be obtained. Why is this?
Correct answer: C. The light from the lamps is not coherent.
- A. The lamps are not point sources.
- B. The lamps emit light of different amplitudes.
- C. The light from the lamps is not coherent.
- D. The light from the lamps is white.
Explanation
When light from two separate lamps falls on a screen, interference patterns typically do not form because the light from each lamp is not coherent. In order to observe interference patterns, the light sources need to be coherent, which means that the light waves emitted by the sources have a constant phase difference between them.
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About Superposition and Interference
Superposition states that overlapping waves produce a resultant displacement equal to the algebraic sum of their individual displacements. Interference covers constructive and destructive interference, phase difference, path difference, coherent sources, and conditions for maxima and minima. It differs from diffraction, which involves spreading around openings or obstacles.
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