The widths of the lines produced by monochromatic light falling on a diffraction grating can be reduced by:?
The correct answer is:
increasing the number of rulings without changing their spacing
why? thanks!!
To understand why increasing the number of rulings on a diffraction grating reduces the widths of the lines produced by monochromatic light, we first need to understand the concept of a diffraction grating.
A diffraction grating is a device that consists of a large number of parallel slits or rulings, evenly spaced apart. When monochromatic light passes through a diffraction grating, it undergoes diffraction, which is the bending of light waves around obstacles or through narrow openings.
The key principle behind diffraction is called the Huygens-Fresnel principle, which states that every point on a wavefront acts as a source of secondary spherical waves. When these secondary waves interfere with each other, they create constructive and destructive interference patterns, resulting in the formation of diffraction patterns.
When monochromatic light passes through a diffraction grating, each slit acts as a source of secondary waves. These secondary waves interfere with each other and form a series of bright and dark fringes on a screen located behind the grating. The bright fringes correspond to regions of constructive interference, where the secondary waves reinforce each other. The dark fringes correspond to regions of destructive interference, where the secondary waves cancel each other out.
The spacing between the rulings on a diffraction grating determines the angle at which the incoming light is diffracted. Specifically, the spacing between the rulings affects the angle at which constructive interference occurs for different wavelengths of light.
Now, coming back to the original question, increasing the number of rulings on a diffraction grating without changing their spacing effectively increases the number of sources of secondary waves. This means that more secondary waves will interfere with each other, resulting in a more pronounced interference pattern.
By increasing the number of interference sources, the bright fringes become narrower, while the dark regions become wider. This reduction in the width of the bright fringes ultimately leads to narrower lines being formed when the light is observed on a screen.
Therefore, to reduce the widths of the lines produced by monochromatic light falling on a diffraction grating, you need to increase the number of rulings without changing their spacing.