[ناصر اللحياني]

d



decelaration
negative acceleration - when an object slows down.

تباطؤ


معدل تناقص سرعة الجسم مع الزمن.



Decibel
a unit for measuring the volume of sound. It uses a logarithmic scale, so that a sound of 20dB is ten times louder than one of 10dB and a sound of 30dB is ten times louder again. Measurements of loudness in decibels are usually taken from the threshold of hearing as 0dB. DB (abbr.)

ديسيبل


وحدة لوغاريتمية لقياس الجهاز الصوتية (الصوت الذي جهارته 20 دِيسيبل يكون أعلى 10 مرات من الذي جَهارتُه 10 ديسيبل)




deep inelastic scattering
Scattering of high energy electrons. Fired at protons and neutrons at high energy, and they are scattered inelastically, which leads to theory that the nucleons have a substructure composed of quarks. .
التشتت غير المرن العميق




density
the mass of a body divided by its volume. The density will be the same for any object made of a given material and is a measure of how the mass of a body of a given size depends on the material from which it is made. SI unit: kg m ^-3 , though the non SI unit of gram per centimeter cubed g cm^3.

كثافة


كتلة وحدة الحجم (= الكتلة ÷ الحجم)




diffraction
the spreading out of the wave after it has gone around a solid object or after it has passed through a space between solid objects.

حُيود


انعراج الموجه (أو انتشارها) عند دورانها حول جسم أو عبورها عبر فجوة.




dimension
The relationship between base units and other units.. the power to which the three fundamental units of (mass,length,time)must be raised to brief the unit of a given physical quantity is known as dimension of that quantity .
البعد




diode
any object which allows current to flow in one direction only.

صمام ثنائي


دايُود، يجعل التيار يَسْري في اتجاه واحد.



diopter
the unit in which the power of a lens is measured. A lens with a focal length of one metre will have a power of one dioptre. Converging lenses have positive powers; diverging lenses have negative powers. Also written dioptre.

ديُويْتَر


وحدة قياس قوة العدسة: (= معكوس الطول البؤري بالأمتار)




Dispersion
the difference in deviation for light of different wavelengths, due to the change in refractive index with wavelength.

تشتت، تفرق


تحلل الضوء الأبيض (المتعدد الأطوال الموجية) بالانكسار المتفاوت لموجاته.




displacement
the volume of fluid pushed out of the way when a solid body is placed in the fluid.

إزاحة


حجم المائع المزاح عند غمر جسم صلب فيه.




distance
Distance is the separation between two places. Distance in measured in inches, or feet, or miles, or centimeters, or meters, of kilometers.. A measured amount of space between two (or more) set points.. distance between two points gives how far a body travels from one point to another along a particular path. How far an object moves. .

المسافة



doppler effect
the change in frequency of a sound wave heard when the source of the sound and the listener are moving towards or away from each other.

the effect caused by a source of sound waves moving away or towards the sensor. . THE APPARANT CHANGE IN FREQUENCY WHEN THERE IS RELATIVE MOTION BETWEEN OBSERVER AND THE SOURCE.(APPLIED FOR BOTH LIGHT,SOUND AND ANY E.M. WAVES.. where a sound changes frequency, changing the pitch when the source of the sound is moving away or towards you.
ظاهرة "دُويْلَر"
تُعرف ظاهرة دوبلر على إنها إزاحة للتردد نتيجة للحركة النسبية بين المصدر والمراقب. فعندما يكون المصدر مقترب من المراقب يكون التردد المقاس أعلى من التردد الأصلي أي مزاح ناحية الترددات الأعلى بينما يكون التردد اقل من التردد المقاس أي مزاح ناحية الترددات الأقل إذا كان المصدر مبتعدا عن المراقب. وظاهرة دوبلر تعتمد على السرعة النسبية بين المصدر والمراقب.

Drag
the viscous force which tends to slow down objects moving through a fluid.

السحب


المقاومة (اللزوجية) التي يبديها المائع لجسم متحرك عبره




drift
a magnetically trapped ion or electron moves as if it were attached to a magnetic field line. Drift is one of the features of such motion, namely its slow shift from one magnetic field line to its neighbor. In the Earth's magnetic field, such drifts gradually move particles all the way around Earth. Viewed from far above the north magnetic pole, ions drift around the Earth clockwise, electrons counter-clockwise, resulting in an electric current circling the Earth, the ring current.

انسياق


حركة حاملات التيار الكهربائي، في شبه الموصل، تحت تأثير فلطية مؤثرة.





dynamics
the study of the motion of particles under the influence of forces. Dynamics deals with the causes of motion, as opposed to kinematics which deals with its geometric description

الديناميكا


فرع من علوم الميكانيكا، يختص بالقوى المتحركة أو التي تسبب حركة الأجسام.