Lenses are used to see and visually document the world around us.
The two main types of lenses are convex and concave. They are used in many different tools, reflecting and bending light to produce an image. Lenses work by moving light in different directions using refraction, forming a smaller or larger image. A beam of light may diverge or converge depending on the shape of the lens.
Convex lenses are thick and bulge outwards in the center. Magnifying glasses and microscopes use convex lenses. Rays of light enter one side of the lens and intersect at a spot on the other side of the lens called a focal point. A thicker lens creates a bigger image.
Concave lenses are a thinner lens that curves inward on both sides. Light rays pass through one side of the lens and spread out than convex lenses and curve in a manner exactly on the other side – opposite of a convex lens. Concave lenses are often used to help nearsighted people see better.
When looking through a telescope far-away objects, such as constellations, appear closer and brighter. The shape of the lenses and the distance between them change the image they produce. Microscopes takes a small objects, such as cells, and create a bigger image of the object. Both the microscope and telescope use two or more lenses to form an image.
An optical microscope can magnify an image up to 2,000 times the size of the specimen. The powerful objective lens produces a magnified image which is then viewed with an eyepiece lens. A focus knob adjusts how far apart the specimen is from the objective lens. Some microscopes have several different objective lenses with varying powers of magnification. The mirror below the specimen reflects light that illuminates the object.
Convex and concave lenses are very useful in bringing our world into focus.