The little boy can see dead people. One man had past without even knowing and suddenly came to the realization.
Answer:
Glass is the most common material used to construct lens elements, due to its good optical properties and resistance to scratching. Other materials are also used, such as quartz glass, fluorite, plastics like acrylic (Plexiglass), and even germanium and meteoritic glass.
Francisco Ayala<span> – image: “Guernica” by Pablo Picasso
"</span><span>Faith is what religion and science have in common."</span>
