The Young's Experiment Interactive is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom. 

We redid this simulation as Version 2.0 in January of 2022 in response to user feedback. Most negative feedback was answer key related. The redo should solve the ambiguity regarding correct answers. Version 2.1 was made three months later to equip the Interactive with Task Tracker compatibility. Learn more.

We recognize that many may prefer the original version. You can find it here ...
Version 1 Simulation || Version 1 Activity Page


Teaching Ideas and Suggestions:

This Interactive simulates a modern day version of Thomas Young's famous double slit experiment. This classic experiment involves passing sunlight through two closely-spaced slits in a card and projecting the resulting interference pattern onto a distant wall. Three different length measurements allowed Thomas Young to calculate the wavelength of the light. In this modern-day, simulated version, lasers are used as the source of monochromatic light. A front-view of the interference pattern that is projected onto the distant screen can be used to determine the spacing between adjacent bright bands on the screen. Students will need to tap on two bright bands - adjacent or otherwise - to determine the spacing distance and corresponding m value. This provides a value of y and m in the wavelength = y•d/(m•L) equation. Values of d and L are reported on the Interactive. Learners must compute the wavelength of all three lasers to complete the activity. The wavelength value is a multiple of 10. Arrow buttons must be used to set their wavelength answer. Once the value is entered, the answer can be checked. Feedback is immediate. Students can try an infinite number of times. The colors are presented at random to the students. Once a wavelength is correctly calculated, that color is no longer presented to students. Once all three color wavelengths are correctly determined, an on-screen trophy is presented to the students.

The nature of the activity and the feedback that is provided makes this Interactive an excellent summative assessment of student understanding of Young's Experiment. Instructors can simply ask students to show them their screen once they have successfully finished the activity. 

The Physics Classroom has provided a ready-to-use classroom exercise for use with this Interactive. The exercise guides students through both the conceptual and the mathematical analysis of Young's experiment. View Exercise.


Related Resources

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Young's Experiment Interactive. These include:
  • Reading:
    Lesson  3 of the Light and Color Chapter of the Tutorial are perfect accompaniments to this Interactive. The following pages will be particularly useful in the early stages of the learning cycle on light and color:

    Anatomy of a Two-Point Source Interference Pattern

    The Path Difference

    Young's Equation

    Young's Experiment

    Other Applications of Two-Point Source Interference

  • Curriculum/Practice: There are several Concept Development worksheets at the Curriculum Corner on the topic of light and color. None of them specifically address the topic of two-point source interference. However, you will find serveral useful think sheets that pertain to electromagnetic waves and the wave behavior of light.

    Visit the Curriculum Corner.

  • Labwork: 
    Simulations should always support (never supplant) hands-on learning. The Laboratory section of The Physics Classroom website includes several hands-on ideas that complement this Interactive. Three notable lab ideas include ...

    Ripple Tank Lab
    Two-Point Source Analysis Lab
    Young's Experiment Lab

    Visit The Laboratory.

Additional resources and ideas for incorporating the Young's Experiment Interactive into an instructional unit on Light and Color can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.


The Physics Classroom would like to extend a special thanks to Nerd Island Studios for the creation of the original version 1 of this HTML5 Interactive. Visit to see more great stuff by Nerd Island Studios. We redid the simulation in January of 2022 in response to user feedback. Most negative feedback were answer key related. The redo should solve the ambiguity regarding correct answers. There may be some who would still like to use the Version 1 simulation. You can find it here ...

Version 1 Simulation || Version 1 Activity Page.

Visit: Interactive | Exercise


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