through the principal focus after refraction (by a lens) or reflection (by a mirror). Sec.why another ra ' joining the top of the ubje tanu the pole o the lens is draw... such a ray passes through the center of the lens with.t Jnuergoing an, we ation For a curved mirror a ray oilIng the top of the object and the center o. Cr ature is drawn . ha ray is re e_ted al_..g the sa e path. Lastly he point in which the two rays in erse t is the position c. the image, a line erpenuicular : he principal ads is drawn to mark the po ition o the inage