To obtain greater dispersion by a diffraction grating:
Correct answer: D. The slit separation should be decreased
- A. The slit width should be increased
- B. The slit width should be decreased
- C. The slit separation should be increased
- D. The slit separation should be decreased
Explanation
The correct answer is to decrease the slit separation. In a diffraction grating, narrower slit separation results in larger angular separation between different diffraction orders. This larger angular separation increases the dispersion, allowing different wavelengths of light to be spread out more effectively. Conversely, increasing the slit separation reduces the angular spread and thus decreases dispersion. Increasing or decreasing the slit width primarily affects the intensity and sharpness of the diffraction pattern, not the dispersion.
This question appeared on the ETEA MDCAT 2016 paper, which you can sit online with every answer explained.
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Light is studied through reflection, refraction, dispersion, interference, diffraction and polarization, linking ray behavior with its wave nature. Questions may involve mirrors, lenses, optical instruments, refractive index and image formation, while geometrical optics deals with rays and wave optics explains effects such as interference and diffraction.
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