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(a) Observer's view of the apparatus. The pair of boxes are lined with the same materials but the lights in them differ spectrally. Three of the objects are made from the same material (Standards), while one is made from a material of a different color (Test). Observers (and readers) are asked to pick the object number corresponding to the odd material. (b) Another view of the apparatus. The Test is now under a different light than in the panel above.
