Chinese English

In ASTRONOMY, the apparent displacement in position of a HEAVENLY BODY caused by the combination of the VELOCITY of light and that of an observer on the surface of the EARTH. Aberration of light due to the ROTATION of the EARTH on its AXIS is termed diurnal aberration. That due to the REVOLUTION of the EARTH around the SUN is termed annual aberration. In optics, failure of an OPTICAL SYSTEM to bring all LIGHT RAYS received from a point object to a single IMAGE POINT or to a prescribed geometric position. Spherical aberration is caused by RAYS from various zones of a LENS or MIRROR coming to FOCUS at different distances from the LENS or MIRROR. Chromatic aberration (or chromatism) is due to the differences in REFRACTION of the coloured RAYS of the SPECTRUM; those of each colour having a different FOCUS.

在天文学中，指光速及地面观测者的速度综合引起的天体位置视位移。由地球自转所引起的光行差，称为周日光行差（diurnal aberration），由地球公转引起的光行差，称周年光行差（ annual aberration）。 在光学中，指光学系统未能将点状目标接收的全部光线变为单一的像点或投射到预定的几何位置。若由球面反射镜或透镜来的光线到光轴的距离变化时，其焦距也跟着变化，则所产生的像差为球面像差（Spherical aberration ）；由于透镜材料使不同颜色的光线折射率不同而聚焦到不同的位置所产生的图像色纹称为色差（chromatic aberration）。

The faculty of the human eye to adjust itself to give sharp IMAGES for different object distances. In STEREOSCOPY, the ability of the eyes to bring two IMAGES into superimposition for stereoscopic viewing.

The gradual building up of LAND over a long period of time, solely by the action of the forces of nature, on a BEACH by deposition of water or air-borne material. Artificial accretion is a similar build-up of LAND by reason of an act of man. Also called aggradation.