Which mirror does have a real focus?
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Real Focus in Mirrors
In optical systems, a concave mirror is the type of mirror that has a real focus. When parallel rays of light incident upon the reflecting surface of a concave mirror, they converge after reflection and meet at a point in front of the mirror. This common point of convergence is known as the principal focus or focal point, and it is real because the light rays actually pass through this point after reflection.
Concave Mirrors
Concave mirrors, also known as converging mirrors, have a reflective surface that curves inward, resembling a portion of the interior of a sphere. These mirrors condense light and are used in various applications where focusing light is necessary, such as in telescopes, headlights, and solar concentrators.
Properties of the Real Focus
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- The focus of a concave mirror is real and can be projected on a screen. ", "
- It is located along the principal axis, the straight line passing through the center of the mirror's surface. ", "
- The distance between the mirror's surface and the focal point is called the focal length. ", "
Convex Mirrors
In contrast, convex mirrors, or diverging mirrors, have a reflective surface that bulges outward. They cause parallel light rays to diverge, and the rays appear to come from a point behind the mirror. This point is referred to as a virtual focus because the light rays do not actually meet but only appear to do so when the rays are extended backward.
Focal Length Determination
To find the focal length of a concave mirror, you can use the mirror equation (1/f = 1/do + 1/di) or perform a simple experiment with a distant light source, aligning the mirrored rays onto a screen to determine the point of focus.
In summary, a concave mirror has a real focus because it causes parallel incident light rays to converge at a singular point after reflection, which is practically observable and measurable.