![]() They just happen to pass through this point and continue their journey on into the universe. NOTE: The light rays do not stop when they get to the focal point. Finally, lasers are a relatively inexpensive source of parallel light due to their inherent nature. Objects that are a great distance away like hills or trees may also furnish almost parallel rays. So sunlight is a convenient source of parallel light rays. If the object is very far, say 93,000,000 miles (1.5 x 1011 m) like the Sun, the distance is sufficiently far that light rays are essentially parallel. Depending on the focal length of the specific lens, this distance might be anywhere from a few meters to a kilometer. If an object is very far away, the angle formed between adjacent light rays is very small. Now the question is where one would find parallel light rays in nature? How common or uncommon are parallel light rays if most of the light we seen on a daily basis is diverging to one degree or another? The distance from the lens to this point is called the focal length of the lens.īecause it seems rather odd to represent light as a dark line on a white page, the diagram above has been inverted below to show white light on a black background. The focal point of a convex lens is the point where light rays parallel to the axis are brought to a point. Now with convex lenses, the sides are continuously curved allowing the light to be focused into a point rather than a larger area. The area where the light rays are converged is called the focal area. If the angles are calculated correctly, light rays which are parallel to one another when approaching such an arrangement can be brought together in a small area as illustrated here: Light passing through the angled prisms near the edges is bent significantly while light passing through the flat, central area is hardly bent at all. One such is shown here and is called a Fresnel Lens. In fact, a stack of prisms of varying angles can be used to simulate the actions of a convex lens. When we look at the cross-section of a convex lens we notice that the edges resemble prisms. Rather a very specific definition is used to define this important property of convex lenses.įirst, a convex lens is one which is thicker in the center than it is near the edges. Many people mistakenly think that the place where images are formed is the focal point. In this section we deal with a very important aspect of convex lenses, namely focal point. ![]() Focal Point - Convex Lenses Focal Point - Convex Lenses
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