Lesson: Two-Slit Interference Physics • 9th Grade

In this lesson, we will learn how to calculate the positions of points of maximum and minimum intensity in interference patterns generated by double slits.

Lesson Plan

Lesson Video

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17:41

Lesson Explainer

Sample Question Videos

  • 06:21

Lesson Worksheet

Q1:

Light with a wavelength of 636 nm passes through a sheet in which there are two parallel narrow slits. The light from the slits is incident on a screen parallel to the sheets, 1.08 m away, where a pattern of light and dark fringes is observed. A line 𝐿 runs perpendicular to the surface of the sheet and the direction of the slits. The line 𝐿 intersects the central bright fringe of the pattern on the screen. The distance on the screen from 𝐿 to the center of the bright fringe nearest to the central bright fringe is 6.11 cm. What is the distance between the slits? Give your answer to two decimal places in scientific notation

Q2:

Light with a wavelength of 597 nm passes through a sheet in which there are two parallel narrow slits 7.64 μm apart. The light from the slits is incident on a screen parallel to the sheet, where a pattern of light and dark fringes is observed. A line 𝐿 runs perpendicular to the surface of the sheet and the direction of the slits, intersecting the central bright fringe of the pattern on the screen. Two lines, line I and line II, intersect 𝐿 at the position of the sheet. Line I intersects the center of the dark fringe closest to the central bright fringe and line II intersects the center of the bright fringe closest to the central bright fringe. Both lines I, and II are on the same side with respect to line 𝐿. What is the angle between line I and line II? Give your answer to one decimal place.

Q3:

Which of the following formulas correctly relates the angle 𝜃 at which light with a wavelength 𝜆 emerges from a pair of narrow slits separated by a distance 𝑑 to the order 𝑛 of a bright fringe of an interference pattern produced by the light on a screen?

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