ABOUT FOSSILS: Fossils are the remains of organisms like plants or animals that have been preserved through time, usually found buried within thick layers of sedimentary rock. Sedimentary rock is formed as new layers are added, one over the other, over time, with fossils from that specific time period forming within each layer. Because they occur in chronological order in rock formations, the fossil record is like Earth's diary. When an organism dies, it gradually breaks down so that soft tissue, muscle and internal organs decompose. However bones and teeth are more likely to be preserved, especially if buried under sediment. As the material decays over time, minerals dissolved in surrounding groundwater can seep in. The object maintains its original shape, but is now composed of hard minerals: a fossil.
HOW DO MICROSCOPES WORK? A light source is typically required to illuminate a specimen. And a tube that holds the eyepiece at the proper distance from the lens is needed. A lens is simply a curved piece of glass that takes the beams of light bouncing off an object and redirects them to a focal point, forming an image that looks exactly like the object in front of the lens. Because light travels faster through air than it does through glass, the lens slows it down. When light enters a piece of glass at an angle, one part of the wave will reach the glass before another and will start slowing down. Depending on the angle at which it enters, the light bends in one particular direction. It bends again when it exits the glass, as parts of the light wave enter the air and speed up before other parts. This is called refraction. In a concave lens, one or both sides of the glass curves inward, causing light to spread out, like a wave. In a convex lens, one or both sides of the glass curves out, so that rays of light passing through will bend toward the center of the lens to focus it to a single point. In a microscope, a concave lens gathers light from the specimen. Because the sample is small and nearby, very little light is needed for the task, so the concave lens is small and curved, giving it a shorter focal length on either side. This brings the specimen into focus at a short distance with the microscope's tube. The image is then magnified by a second, convex lens as it is brought to the eye.