What do you understand by ‘after images’? Briefly explain.
The effect of a visual stimulus persists for some time even after the removal of that stimulus from the visual field. This effect is called ‘after image’. After images are positive and negative. Positive after images resemble the original stimulus in terms of hue, saturation and brightness. They usually occur after a brief intense stimulation of dark adapted eyes. On the other hand, negative after images appear in complementary colours. These images appear when a person stares at the patch of a particular colour for at least 30 seconds, and then transfers the gaze to a neutral background. For example - if the person looks at the blue colour the negative after image will appear in yellow.
