أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ٧_ e

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 7_ E


evaporation
evaporation f

Evaporation. The escape of particles from a solid or liquid surface so that they form vapor.vapour. This can only happen if the particles have high energy and are on the surface and moving correctly. Therefore, during evaporation, a transfer of energy occurs from the substance and its temperature tends to decrease. This also increases the rate of evaporation with increasing temperature and entails heat, see boiling point.


expansion
dilatation f

Stretch. A change in the volume of samples of a substance resulting from a change in temperature. A rise in temperature means a rise in the average energy of particles (see kinetic model), so they move more quickly and try to occupy more space. The effect is greater in the case of gases (see gas laws), which all expand at approximately the same rate when exposed to the same increase in temperature. The expansion of solids and liquids is much less, but their “expansivity” varies greatly from one substance to another. See - bi metal strip and see also water, expansion of.

The expansion of a substance is the increase in unit volume of a sample for a unit change in temperature. (The word here refers to the length of the volume or area of ​​solid bodies and to volume for solids, liquids and gases). The unit here is in degrees, or in kelvins.
So :

Linear expansion = length increase / original length x temperature rise
I/Lo = a
Thermal expansion has many uses, such as in thermometers and thermostats. This expansion may be a problem in structures such as clocks, roads, and bridges.


eye
oeil m

eye . A sensory organ that responds to visible light. The eyeball occupies a cavity in the skull, and a number of muscles can move this ball. The eyelid protects the eye, while tears secreted by one of the glands keep the front of the eye exposed to the outside environment clean and moist.

Light passes through the cornea (a) in the drawing below into a space filled with liquid. The “lens” (c) remains in its position thanks to a circular muscle, the ciliary muscle (d). The lens changes its shape to transmit light coming from objects located at different distances (accommodation). See vision defects. The colored “iris” (b) is also a circular muscle, and it opens or closes to change the amount of light passing through the central hole, the pupil. The space behind the lens is filled with a gelatinous substance, which helps maintain the shape of the eyeball.

Light reaching the layer of nerve cells forming the retina (e) is absorbed. The energy of this light is transformed into signals that pass to the brain through the optic nerve (and). See also col our vision and optical instruments.