basic purpose of this lecture is to Presentation on X-Ray and Computed Tomography. In normal case, an X-ray imaging system requires X-Ray Source, a patient to image, Film also called image receptor and Radiologist/Diagnostician. Here briefly discuss on these X-ray imaging system. Tomography is Problem in X-ray which visualizing the details of the interior of the human body or other objects. Finally discuss and analysis on Beer’s law or Beer–Lambert law and 2D Planar X-ray. Here explain all process of X-Ray and Computed Tomography with picture and examples.