What value indicates pure 546 nm in the mixture field of the Nagel Anomaloscope?

The correct value indicating pure 546 nm in the mixture field of the Nagel Anomaloscope is 0. This is significant because the Nagel Anomaloscope is specifically designed to assess color vision and the ability to match colors. In its operation, one field presents a pure green light (546 nm) and the other field allows for the addition of red light to create color mixtures.

When the mixture field is adjusted to the value of 0, this signifies that there is no addition of red; hence, only the green light at 546 nm is present. This is critical for determining the threshold at which an individual perceives color differences accurately and is used in testing for color vision abnormalities such as red-green color deficiencies.

Understanding this setup helps to appreciate how the Nagel Anomaloscope measures an individual’s ability to distinguish between different colors and how the level of red is adjusted to match the pure green light.