Compare between Convex lens and concave lens

A convex lens or converging lens focuses the light rays to a specific point whereas a concave lens or diverging lens diverges the light rays. When these lenses are combined, they produce sharper images. Most of the eyeglass lenses use combinations of convex and concave lenses.

the device is called “ rocket engine”

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.