Concave mirror - Oumenkyo

Japanese: 凹面鏡 - おうめんきょう

In the narrow sense, a mirror whose reflecting surface is the inside of a sphere. If the focal length f is half the radius r of the sphere, and the distances from the mirror to the object and image are a and b, respectively, the relationship in (Equation 1) holds. If the object is farther away from the mirror than the focal point, an inverted real image will be formed on the same side as the object, and if it is closer than the focal point, an upright virtual image will be formed on the opposite side of the object. In the broad sense, this includes parabolic mirrors, whose reflecting surface is the inside of a paraboloid of revolution, and ellipsoidal mirrors, whose reflecting surface is the inside of an ellipsoid of revolution. They reflect parallel rays so as to converge. → Convex mirror → Related items Mirror | Spherical mirror

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

狭義には球面の内側を反射面とする鏡。焦点距離fは球面の半径rの半分で，鏡から物体，像までの距離をそれぞれa，bとすると，（式１）の関係がなりたつ。物体が鏡から見て焦点より遠ければ，物体と同じ側に倒立の実像ができ，焦点より近ければ，物体と反対側に正立の虚像ができる。広義には回転放物面の内側を反射面とする放物面鏡，回転楕円面の内側を反射面とする楕円面鏡を含む。平行光線を収束させるように反射する。→凸面鏡
→関連項目鏡｜球面鏡

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