In a Young's double slit experiment, the source is white light. One of the slits is covered by red filter and another by green filter. In this case,
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- There shall be alternate interference fringes of red and green.
- There shall be an interference pattern, where each fringe's pattern center is green and outer edges is red.
- There shall be an interference pattern for red distinct from that for green.
- There shall be no interference fringes.
The Correct Option is D
Approach Solution - 1
In a Young's double slit experiment, interference occurs when light waves from two coherent sources overlap, producing constructive and destructive interference patterns. For this interference to be visible, the sources must be coherent and monochromatic.
- Light Perception: White light consists of multiple wavelengths. If filters are used, red and green in this case, each slit allows only one specific color (wavelength) to pass.
- Red and Green Light: When one slit is covered by a red filter and the other by a green filter, different wavelengths (colors) are made to interfere.
- Lack of Coherence: Red and green light do not originate from a single source and hence are incoherent. In order for interference fringes to be visible, the light waves from both slits should be of the same wavelength and coherent.
- Conclusion: Due to the incoherence and different wavelengths of red and green light, they will not produce a stable interference pattern. The overlapping of these non-coherent waves results in a lack of any distinct interference fringes.
Thus, the correct answer is: There shall be no interference fringes.
Approach Solution -2
In Young's double-slit experiment, the interference pattern is formed when the waves from two slits combine.
When white light passes through two slits, it forms a pattern of colored fringes because the different colors (wavelengths) interfere differently, leading to a spectrum of colors.
Now, if one slit is covered with a red filter and the other with a green filter:
- The red filter allows only red light to pass through the first slit.
- The green filter allows only green light to pass through the second slit.
Since red and green light have different wavelengths, they will produce separate interference patterns.
However, these patterns will not overlap or interfere with each other.
The red light from one slit and the green light from the other will not create a combined interference pattern.
Thus, there will be no interference fringes as expected from a single wavelength of light.
Instead, we see two independent interference patterns for red and green light.
Therefore, the correct answer is Option (4) — There shall be no interference fringes.
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