An optometrist prescribes a corrective lens with a power of +1.5 diopters. The lens maker will start with glass blank with an in
dex of refraction of 1.6 and a convex front surface whose radius of curvature is 20 cm. To what radius of curvature should the other surface be ground?
Answer: Elements in the same period have the same number of electron shells; moving across a period ( elements gain electrons and protons and become less metallic. This arrangement reflects the periodic recurrence of similar properties as the atomic number increases.