Dr. Ahmed G. Abo-Khalil

Electrical Engineering Department

coherent light

In physics, coherence is an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference. It contains in fact several distinct concepts, which are limit cases that never occur in reality but allows to understand the physics of waves and has become in particular a very important concept in quantum physics. More generally, coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets. One should note at this point that interference is nothing more than the addition, in a mathematical sense, of wave functions. In quantum physics, a single wave can interfere with itself, but this is due to its quantum behavior and is still an addition of two waves (see Young's slits experiment). This implies that constructive or destructive interferences are limit cases, and that waves can always interfere, even if the result of the addition is complicated or not remarkable.

When interfering, two waves can add together to create a wave of greater amplitude than either one (constructive interference) or subtract from each other to create a wave of lesser amplitude than either one (destructive interference), depending on their relative phase. Two waves are said to be coherent if they have a constant relative phase. The degree of coherence is measured by the interference visibility, a measure of how perfectly the waves can cancel due to destructive interference.

Temporal and Spatial Coherence can be exhibited by Michelson–Morley experiment and Young's slits experiment respectively. Once the infringes are obtained in Michelson–Morley experiment, if now one of the mirror is moved away gradually then the time for the beam to travel increases and the infringes become dull and finally are lost, showing Temporal Coherence. Similarly if in Young's double slit experiment if the space between the two slits is increased, the coherence dies gradually and finally the infringes disappear , showing Spatial Coherence.

Office Hours

No office hours

My Timetable


email: [email protected]

[email protected]

Phone: 2570


Welcome To Faculty of Engineering

Almajmaah University




Links of Interest





Travel Web Sites






ستقام اختبارات الميدتيرم يوم الثلاثاء 26-6-1440

حسب الجدول المعلن بلوحات الاعلان

Summer training

The registration for summer training will start from 5th week of second semester

Academic advising

Class registration week 1

برنامج التجسير

إحصائية الموقع

عدد الصفحات: 2879

البحوث والمحاضرات: 1280

الزيارات: 99440