The distance between the maxima of two wavelengths seen on a screen, a...
The correct answer is: decreases as the number of slits per cm increases
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The distance between the maxima of two wavelengths seen on a screen, a...
Explanation:
When light passes through a diffraction grating, it undergoes diffraction, resulting in the formation of a pattern of bright and dark fringes on a screen. The maxima in this pattern occur at specific angles, which are determined by the wavelength of light and the spacing between the slits on the grating.
Interference and Diffraction:
Before understanding the effect of the number of slits per cm on the distance between the maxima, let's briefly review interference and diffraction.
- Interference is the superposition of two or more waves, resulting in constructive or destructive interference.
- Diffraction is the bending or spreading of waves as they encounter an obstacle or pass through a narrow opening.
Effect of the Number of Slits per cm:
When a beam of light passes through a diffraction grating, it is diffracted by each individual slit. The diffracted waves then interfere with each other to form a pattern of bright and dark fringes on a screen.
- The spacing between the slits on the grating determines the angle at which the diffracted waves interfere constructively and form bright fringes.
- The distance between the maxima (bright fringes) depends on the angle of diffraction, which is related to the wavelength of light and the spacing between the slits.
- As the number of slits per cm on the grating increases, the spacing between the slits decreases.
- According to the diffraction grating equation, which relates the angle of diffraction to the wavelength and the spacing between the slits, if the spacing between the slits decreases, the angle of diffraction increases for a specific wavelength.
- Since the distance between the maxima is directly related to the angle of diffraction, an increase in the angle of diffraction results in an increase in the distance between the maxima.
Conclusion:
Therefore, the distance between the maxima of two wavelengths seen on a screen, after passing through a diffraction grating, increases as the number of slits per cm increases. This is because the decrease in the spacing between the slits leads to an increase in the angle of diffraction, which in turn increases the distance between the maxima. So, the correct answer is option 'B'.