How does the width of the slits affect the intensity in diffraction?

Asked By: Janosne Tzaregradsky | Last Updated: 7th May, 2020
Category: science physics
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Video Explanation. (a) In a single slit diffraction experiment, if the width of the slit is made double the original width, then the size of the central diffraction band reduces to half and the intensity of the central diffraction band increases up to four times. Thus, the diffraction angle will be very small.

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Furthermore, how does the width of the slits affect the intensity?

In single slit diffraction calculations, the resultant amplitude is obtained by dividing the slit width into a large number of equal segments. So amplitude should be proportional to slit width. The intensity is proportional to the square of slit width, as intensity is proportional to the square of the amplitude.

Also Know, what is the relation between intensity and fringe width? It depends upon the wavelength or frequency of light. Intensity of the incident light has no relation with the fring width in any case. It's the measure of the power incident on a surface per unit area. The brightness of the fringes are affected by intensity of incident light not the fringe width.

Secondly, how does the width of the slits affect the interference pattern?

The separation of the interference fringes depends on the slit separation. If now the slit width is increased the width of the diffraction envelope is decreased whilst the separation of the interference fringes stays the same. So less interference fringes will be visible.

What happens when you increase the number of slits in a diffraction grating?

The grating intensity expression gives a peak intensity which is proportional to the square of the number of slits illuminated. Increasing the number of slits not only makes the diffraction maximum sharper, but also much more intense. Such a multiple-slit is called a diffraction grating.

24 Related Question Answers Found

What is the formula for fringe width?

Given: Distance between images = d = 0.6 mm = 0.6 x 10-3 m = 6 x 10-4 m. Distance between source and screen = D = 1.5 m, Fringe width = X = (3/20) cm = 0.15 cm = 0.15 x 10-2 m = 1.5 x 10-3 m. To Find: Wavelength of light used = λ =?

How do you measure the distance between slits?

In my book'a section on Young's double-slit experiment, the formula, d=mλsinθ, is given. In this equation d is the distance between two slits, λ is the wavelength of light coming through the slits, and θ is the angle between the central reference to the brightest maximum on the screen opposite the slits.

What is the width of the central maximum?

This is consistent with the fact that light must interact with an object comparable in size to its wavelength in order to exhibit significant wave effects such as this single slit diffraction pattern. We also see that the central maximum extends 20.7º on either side of the original beam, for a width of about 41º.

How does the number of slits affect the interference pattern?

How does the number of lines or slits in a diffraction grating affect the width of interference maxima? As the number of slits is increased, the width of the maxima decreases (and they get brighter).

What is fringe width?


Fringe width is the distance between consecutive dark and bright fringes. It is denoted by 'β'. In case of constructive interference fringe width remains constant throughout. It is also known as linear fringe width.

Why monochromatic light is used in interference?

Monochromatic light is light of a single wavelength, or at least very narrow bandwidth. That is, all the photons in the light are in phase across the beam and the phase changes smoothly along the beam. This means that the interference pattern is stable, not moving around as different phase photons interfere.

What is Fraunhofer diffraction pattern?

Fraunhofer diffraction is the type of diffraction that occurs in the limit of small Fresnel number . In Fraunhofer diffraction, the diffraction pattern is independent of the distance to the screen, depending only on the angles to the screen from the aperture.

Why is the central fringe twice as wide?

the central fringe is twice as wide as each of the outer fringes (measured from minimum to minimum intensity), the peak intensity of each fringe decreases with distance from the centre, each of the outer fringes is the same width, the outer fringes are much less intense than the central fringe.

What is fringe width in interference?

The dark fringe width can be assumed to be distance between upper points of the two consecutive crest like shapes (see the below figure, it is the wave, but you can imagine it to be interference pattern), it mean the same as saying distance between the centers of two consecutive bright or dark fringe.

How is intensity related to wavelength?


Intensity of light is proportional to energy of light, which is proportional to frequency of light (and number of photons). Frequency of light is inversely proportional to wavelength of light. Thus, intensity is inversely proportional to wavelength, if other variables are held constant.

What happens when the number of rulings in a grating is increased?

If we increase the number of lines of grating, correspondingly the grating element (a+b) decreases , hence diffraction angle becomes large for given wave length . But, then there is limit on number of lines, because sin(theta) should not become greater than 1.

What is grating constant?

For a diffraction grating, the grating constant is the number of lines (or slits) per unit length (eg lines per cm). Thus, the distance between the grating lines is 1/grating constant.

How does the spacing between maxima change when you introduce more slits?

A diffraction grating is a large number of evenly spaced parallel slits. Maxima can be produced at the same angles, but those for the diffraction grating are narrower and hence sharper. The maxima become narrower and the regions between darker as the number of slits is increased.

How does a diffraction grating work?

A diffraction grating is an optical element, which separates (disperses) polychromatic light into its constituent wavelengths (colors). The polychromatic light incident on the grating is dispersed so that each wavelength is reflected from the grating at a slightly different angle.

What happens when white light passes through a diffraction grating?


Like a prism, a diffraction grating separates the colors in white light to produce a spectrum. With a transmission type diffraction grating, light waves are diffracted as they pass through a series of equally spaced narrow openings. (A similar effect takes place if light is reflected from a reflecting grating.)

What is diffraction grating D?

In this formula. is the angle of emergence (called deviation, D, for the prism) at which a wavelength will be bright, d is the distance between slits (note that d = 1 / N if N, called the grating constant, is the number of lines per unit length) and n is the "order number", a positive integer (n = 1, 2, 3, )

Does the distance between interference maxima increase decrease?

As slit separation d increases, the distance between maxima decreases. 2. When slit width is increased, distance between minima is decreased.