Mirrors and Lenses

• A converging lens focuses parallel rays to a point called focal point (F).
• Reflection is the bouncing of light rays when they hit a surface like a plane mirror.
• Plane mirrors exhibit regular or specular reflection, where the angle of incidence is equal to the angle of reflection.
• Specular reflection is the reflection of smooth surfaces, such as plain, shiny surfaces.
• Irregular or diffuse reflection illuminates shaded areas such as under the trees and inside buildings.
• Diffuse reflection is the reflection of rough surfaces, which is observed in objects with irregular surfaces like rocks and buildings.
• The law of reflection states that the angle of incidence is equal to the angle of reflection.
• The angle of incidence is measured between the normal line and the incident ray, while the angle of reflection is measured between the normal line and the reflected ray.
• The resulting reflected image can be characterized according to image orientation, location, size, and magnification.
• The image distance and image size are determined using the mirror equation: 1 over f equals 1 over p plus 1 over q, where f is the focal length, p is the distance of the object from the mirror, and q is the distance of the image from the mirror.
• A 5 centimeter tall light bulb is placed at a distance of 45 centimeters from a concave mirror having a focal length of 10.5 centimeters.
• The magnification equation is h with an apostrophe over h equals negative q over p.
• h with an apostrophe is the height of the image, it is positive if the image is upright, and negative if the image is inverted.
• Focal length is positive if the mirror is concave and negative if it is convex.
• The distance of the image from the mirror is positive if the image is real and located in front of the mirror, and it is negative if the image is virtual and located behind the mirror.
• Magnification is the ratio of the image dimensions to the object dimensions.
• An image may be real or virtual, with a real image formed when rays converge and a virtual image shown when rays only appear to diverge.
• The orientation of an image can be upright if it is right side up and inverted if it is upside down.
• The location of an image always depends on the location of the object.
• A meter is a carefully ground or molded piece of transparent material that refracts light rays in such a way that it forms an image.
• A convex lens is a lens that converges rays of light that are traveling parallel to its principal axis.
• The point where light converges in a convex lens is called the focal point, which is denoted by the letter f.
• Light rays that incident towards either face of the lens and traveling parallel to the principal axis will either converge or diverge for convex lenses.
• A concave lens is a lens that diverges rays of light that are traveling parallel to its principal axis.
• Technically, a lens does not have a center of curvature, but it does have an imaginary point that we refer to as 2f point.
• Converging lenses can be identified by their shape, which is relatively thick across their middle and thin at their upper and lower edges.
• Each lens has two focal points one on each side of the lens, unlike mirrors, lenses allow light to pass through either face depending on where the incident rays are coming from.
• If the light rays diverge as in a concave lens, the diverging rays can be traced backwards until they intersect at a point, which is known as the focal point of a concave lens.
• Diverging lenses can also be identified by their shape, which is relatively thin across their middle and thick at their upper and lower edges.
• A line passing through the exact center of the lens is known as the principal axis.
• A lens also has an imaginary vertical axis that bisects the symmetrical lens into halves.
• Each lens has two possible 2f points when the object is located at a location beyond the 2f point, the image will always be located somewhere in between the 2f point and a focal point on the lens.
• The size of an image may be larger, smaller, or the same with a magnification of greater than 1, lesser than 1, or equal to 1 respectively.
• In plane mirrors, the image is laterally inverted and has a magnification of one, meaning the image and the object in plane mirrors have the same characteristics except that the image is seen as laterally inverted.
• Lateral inversion is a phenomenon where the left side of the object appears to be on the right side of the reflected image and vice versa, due to the direction that light follows when it strikes a reflecting surface.
• Reflection on curve mirrors is different from reflection on plane mirrors, with a curved mirror being a reflecting surface that is a section of a sphere.
• There are two kinds of curved mirrors: convex and concave, with a spoon being a kind of curved mirror with a concave side and a convex side.
• A line passing through the exact center of a concave mirror is known as the principal axis, the point in the center of the sphere from which the mirror was sliced is known as the center of curvature and is denoted by the letter c, and the point on the mirror surface where the principal axis meets the mirror is known as the vertex and is denoted by the letter a.
• When the object is located at a location beyond the center of curvature, the image will always be located somewhere in between the center of curvature and the focal point regardless of exactly where the object is located.
• In concave lenses the location of the object does not affect the characteristics of the image the resulting image will always be smaller than the object with a magnification less than one.