Some newly married friends were visiting us when the topic of children came up. The bride said she wanted three children, while the young husband said two would be enough for him.
They discussed this discrepancy for a few minutes until the husband thought he`d put an end to things by saying boldly, "After our second child, I'll just have a vasectomy."
Without a moments hesitation, the bride retorted, "Well, I hope you'll love the third one as if it's your own."
Achromatic lensesIn 1758, optician John Dolland, having created achromatic lenses, reported this to the Royal Society. Isaac Newton had described the blurring effect due to chromatic abberation, but could not solve the problem in simple lenses, which was important in the preparation of lenses for telescopes and microscopes. A concave face of a lens of flint glass (which has a greater color dispersion than crown glass) is cemented to a convex face of a crown glass lens. Thus the dispersion properties causing chromatic aberration are removed from both lenses simultaneously. Although Dollond patented the discovery of the achromatic lens in the mid-18th century, it is widely believed that he was not its inventor, but learned about it from lens maker George Bass. |
