Irradiation

Irradiation is an effect of bright light on the retina of the eye. When a bright object is viewed its image is confined to a small area of the retina, but the effect of the disturbance of this area is not quite confined to this limit. The neighbouring parts of the retina may also be disturbed, apparently by some sort of sympathetic action analogous to that of resonators in acoustics. Thus the brain receives the impression of an object larger than it actually is. This accounts for the greater apparent size of the sun when seen in a clear sky than when viewed through a fog. The thickness of the filament of an electric lamp when incandescent appears greater than when cold. Slenderness of a person may be disguised by white apparel, and vice versa. The photograph of a lightning flash always makes it took much smaller than it naturally appears to be.