A triple-slit experiment consists of three narrow slits, equally spaced by distance and illuminated by light of wavelength . Each slit alone produces intensity on the viewing screen at distance .
Consider a point on the distant viewing screen such that the path-length difference between any two adjacent slits is . What is the intensity at this point? What is the intensity at a point where the path-length difference between any two adjacent slits is ?
At this time, the intensity is
When the path-length difference of two adjacent slits at the intensity is
The light casts a shadow when the widths of the slits are greater than the wavelength of the light. Light diffraction occurs when the slit widths are small, and the light waves overlap on the screen. As a result, the light intensity rises as the slit width rises.
If the direction difference between any two adjacent sources is , all three sources' light will be in phase. As a result, the intensity will be
If any two neighbouring slits have a path difference of , two of them will cancel each other out, resulting in the intensity emanating from a single slit, which is,
So, the values are equal.
You've found an unlabeled diffraction grating. Before you can use it, you need to know how many lines per it has. To find out, you illuminate the grating with light of several different wavelengths and then measure the distance between the two first-order bright fringes on a viewing screen behind the grating. Your data are as follows:
Use the best-fit line of an appropriate graph to determine the number of lines per .
FIGURE Q33.1 shows light waves passing through two closely spaced, narrow slits. The graph shows the intensity of light on a screen behind the slits. Reproduce these graph axes, including the zero and the tick marks locating the double-slit fringes, then draw a graph to show how the light-intensity pattern will appear if the right slit is blocked, allowing light to go through only the left slit. Explain your reasoning.
a. Green light shines through a -diameter hole and is observed on a screen. If the hole diameter is increased by , does the circular spot of light on the screen decrease in diameter, increase in diameter, or stay the same? Explain.
b. Green light shines through a -diameter hole and is observed on a screen. If the hole diameter is increased by , does the circular spot of light on the screen decrease in diameter, increase in diameter, or stay the same? Explain.
A student performing a double-slit experiment is using a green laser with a wavelength of . She is confused when the maximum does not appear. She had predicted that this bright fringe would be from the central maximum on a screen behind the slits.
a. Explain what prevented the fifth maximum from being observed.
b. What is the width of her slits?
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