Concave mirrorParabolic mirror。When the parallel light shines on it, it will focus on the focus in front of the mirror through its reflection,ReflectorIs concave,focusIn front of the mirror, when the light source is at the focusLight reflectionPost formationParallel beam, also called concave mirror, convergent mirror.
The principle of concave mirror is reflection imaging.Convex lensIt is refraction imaging, and concave mirror plays the role of light gathering, according toObject distanceDifferent images are different.
Face mirror(Including convex mirror) It is not an instrument that allows light to pass through, but reflects back. Light complies withReflection law of light。
1、Convex lensIt is composed of transparent mirror body ground into spherical surface on both sides
2. Concave mirror is composed of concave mirror on one side and concave mirror on the other sideOpaqueMirror body composition of
Different effects on light
1. Convex lens mainly refracts light
2. Concave mirror mainly reflects light
Different imaging properties
Convex lens is refraction imaging.The image can be inverted and magnifiedReal image, or inverted, isometric, or inverted, reduced, or upright, enlargedVirtual image。
Concave mirror isReflection imaging。The resulting image can be an inverted or enlarged real image, or an inverted or equal sized real image, or an inverted or reduced real image, or an upright or enlarged virtual image.(It looks the same, but it is actually different: the convex lens real image is on the opposite side of the object, the virtual image is on the same side of the object; the concave mirror real image is on the same side of the object, and the virtual image is on the opposite side of the object)
The surface mirror (including convex mirror) is not an instrument that allows light to pass through, but reflects back to image. The light complies withReflection law。
The convex lens can be inverted, enlarged, enlarged or reduced, or magnified verticallyVirtual image。It can also focus the parallel light and refract the light emitted by the focus into the parallel light.Concave mirror has no chromatic aberration because it is reflective imaging, which is an advantage that any lens imaging can not compare with.Resolution andobjective lenseIt is very difficult to manufacture a large aperture lensReflection principleConcave mirrors are much easier to manufacture.
focal length
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Object inConcave spherical mirrorSpherical centerWhen outside, it becomes an inverted and reduced real image, which is located between the focus and the center of the ball;When the object is located between the focus and the center of the sphere, it becomes an inverted magnified real image, and the image is located outside the center of the sphere;When the object is within the focus, it is vertically magnifiedVirtual image, like on the other side of the mirror.No imaging when U=f.
The focal length is behind the front center of the mirror, but not at R/2.But if the incident light isParaxial ray, it can be approximately considered that the focal length is at R/2.
Optical characteristics
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1. The reflection phenomenon on the concave mirror follows the lightReflection law。
2. After the light parallel to the main shaft is reflected by the concave mirror,Reflected lightFocus.The focus of concave mirror is the convergence point of actual light, so it isReal focus。
3. The concave mirror converges the light, so the smaller the focal length, the greater the convergence ability.
4. Four special lights: the light parallel to the main axis is reflected by the concave mirror and converges at the focus;OverfocusIncident lightAfter reflection, it is parallel to the main shaft;The incident light passing through the center of the spherical surface returns along the original path;The ray incident from the vertex is symmetric about the axis with its reflected ray.
