Optics laboratory

Online physics courses need online laboratories.  Here we are developing tools for optics laboratories.  Students will be able to move components on an optical breadboard, align the components, trace a He-Ne laser beam through the system and make measurement.  The app is under development and you can explore the first steps.

Experiment 1:  Reflection and refraction

You are presented with a He-Ne laser, an optical breadboard and several optical components.   The components can be dragged to different positions on the breadboard and the components can snap to the holes on the breadboard which have a spacing of 1 unit = 2.5 cm.  The screen is 4 units wide and 2 units high and the lines on the screen are spaced by ½ unit.  Clicking anywhere on the breadboard you can rotate and zoom the view. Currently, you can steer the laser beam onto a target in three dimensions using two mirrors.  A transparent viewer can help you align the beam.  All components can be translated and rotated, post holders can be raised and lowered, and mirrors can be tilted up and down with the mouse. (Touch has not yet been enabled.)  You can measure the index of refraction of a glass block with dimensions of 2.8 by 2.8 by 1.4 units.

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Click on the image to explore the app!

Experiment 2:  Diffraction and Interference

A He-Ne laser beam (λ = 633 nm) produces Fraunhofer diffraction and interference pattern that you can observe on a screen. You can drag four different slides into the the of the laser beam, and you can vary the slide to screen distance.  Clicking anywhere on the breadboard you can rotate and zoom the view.  The screen and the slides snap to the holes on the breadboard which have a spacing of 1 unit = 2.5 cm.  The screen is 4 units wide and 2 units high and the lines on the screen are spaced by ½ unit.
Three of the slides block all the light except for a single w = 20 μm wide slit, or two or four w = 20 μm wide slits with slit spacing d.  From the observed patterns you can verify the slit width w and determine the slit spacing d.  The only thing blocking the laser light on a fourth slide is a hair.  You can measure the width of the hair using the diffraction pattern produced by the laser light.

The lines on the slides are not drawn to scale.  Their purpose is just to identify the slides.  The most intense regions of the diffraction and interference patterns always have the same maximum color intensity allowed by the computer graphics.  A realistic decrease in the color intensity with distance from the slit(s) would make the dimmer regions of the diffraction and interference patterns invisible at larger distances.  That is a limitation of the computer graphics.

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Click on the image to explore the app!

Experiment 3:  Polarization Lab

The He-Ne laser beam (λ = 633 nm) is unpolarized.  You have 3 (ideal) linear polarizers and a power meter with a Bluetooth connection to a digital readout to monitor the beam intensity.  You can also monitor the intensity of the laser beam on a screen (corrected for the average response of the human eye to light).  The polarizers are mounted in a rotation stage.  The transmission axis of the polarizers is horizontal when the rotation stage reads zero.  You can explore what happens to the transmitted intensity if you rotate a third polarizer between two crossed polarizers and you can verify the Law of Malus.  You can also reflect the laser beam off a glass slide and explore polarization by reflection.  The back of the glass slide is painted black to absorb the transmitted portion of the beam.  The slide is made of high-index of refraction glass, you can measure the index of refraction by finding the  the Brewster angle.

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Click on the image to explore the app!

Suggestions for improvements are welcome.