Intensity Sensor intercepts refracted beam at odd positions

[EthanWJohnson]

Tested on: Chrome, Firefox, Edge, and PhET App

OS: Windows 10 and iOS 10.0.1

Best explained via gif;

The lower part of the intensity sensor can intercept the lower beam, even when not touching it, from above.

Strange positioning for intercept affects all refraction indexes, but is most pronounced when the lower material has a high refraction index.

Bug/issue is also present on the sim currently on the website.

RELATION: phetsims/tasks#682

Troubleshooting information (do not edit):
Name: ‪Bending Light‬
URL: http://www.colorado.edu/physics/phet/dev/html/bending-light/1.1.0-rc.1/bending-light_en.html
Version: 1.1.0-rc.1 2016-08-22 20:48:08 UTC
Features missing: touch
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36
Language: en-US
Window: 1366x648
Pixel Ratio: 1/1
WebGL: WebGL 1.0 (OpenGL ES 2.0 Chromium)
GLSL: WebGL GLSL ES 1.0 (OpenGL ES GLSL ES 1.0 Chromium)
Vendor: WebKit (WebKit WebGL)
Vertex: attribs: 16 varying: 30 uniform: 1024
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 16384x16384
OES_texture_float: true
Dependencies JSON: {"assert":{"sha":"7d27130a","branch":"HEAD"},"axon":{"sha":"1fd91832","branch":"HEAD"},"babel":{"sha":"5e625a61","branch":"master"},"bending-light":{"sha":"09962afa","branch":"HEAD"},"brand":{"sha":"f0b1f7da","branch":"HEAD"},"chipper":{"sha":"136b1d30","branch":"HEAD"},"dot":{"sha":"6e8a26f2","branch":"HEAD"},"joist":{"sha":"ab5582ab","branch":"HEAD"},"kite":{"sha":"88f0c3a0","branch":"HEAD"},"phet-core":{"sha":"c48bf320","branch":"HEAD"},"phetcommon":{"sha":"83ea84c8","branch":"HEAD"},"scenery":{"sha":"0ab22ac3","branch":"HEAD"},"scenery-phet":{"sha":"04cec216","branch":"HEAD"},"sherpa":{"sha":"5ddfccd4","branch":"HEAD"},"sun":{"sha":"061f2ea9","branch":"HEAD"},"tandem":{"sha":"43ebdfb3","branch":"HEAD"}}

[samreid]

@ariel-phet could you help me prioritize/schedule this?

[ariel-phet]

Should be fixed, but marking priority deferred for the moment, until we can get a chunk of @samreid time