Submitted by examrobotsa on Thu, 01/01/1970 - 05:30 The upper and lower portions in common type of bi-focal lenses are respectivelyconcave and convex - convex and concaveboth concave of different focal lengthsboth convex of different focal lengthsquestion_subject: Sciencequestion_exam: CDS-IIstats: 0,38,22,38,6,9,7keywords: {'different focal lengths': [0, 0, 0, 1], 'concave': [0, 0, 0, 4], 'convex': [0, 0, 0, 6], 'common type': [0, 0, 0, 1], 'lower portions': [0, 0, 0, 1]}