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  2. Periscope - Wikipedia

    en.wikipedia.org/wiki/Periscope

    A periscope is an instrument for observation over, around or through an object, obstacle or condition that prevents direct line-of-sight observation from an observer's current position. [ 1 ] [ 2 ] In its simplest form, it consists of an outer case with mirrors at each end set parallel to each other at a 45° angle.

  3. Optics - Wikipedia

    en.wikipedia.org/wiki/Optics

    A ray tracing diagram for a converging lens. A device that produces converging or diverging light rays due to refraction is known as a lens. Lenses are characterized by their focal length: a converging lens has positive focal length, while a diverging lens has negative focal length. Smaller focal length indicates that the lens has a stronger ...

  4. Ray (optics) - Wikipedia

    en.wikipedia.org/wiki/Ray_(optics)

    The principal ray or chief ray (sometimes known as the b ray) in an optical system is the meridional ray that starts at an edge of an object and passes through the center of the aperture stop. [5] [8] [7] The distance between the chief ray (or an extension of it for a virtual image) and the optical axis at an image location defines the size of ...

  5. Retroreflector - Wikipedia

    en.wikipedia.org/wiki/Retroreflector

    Therefore, as the ray reflects first from side x then side y and finally from side z the ray direction goes from [a, b, c] to [−a, b, c] to [−a, −b, c] to [−a, −b, −c] and it leaves the corner with all three components of its direction exactly reversed. Corner reflectors occur in two varieties.

  6. Curved mirror - Wikipedia

    en.wikipedia.org/wiki/Curved_mirror

    A ray drawn from the top of the object to the mirror surface vertex (where the optical axis meets the mirror) will form an angle with the optical axis. The reflected ray has the same angle to the axis, but on the opposite side (See Specular reflection). A second ray can be drawn from the top of the object, parallel to the optical axis. This ray ...

  7. Virtual image - Wikipedia

    en.wikipedia.org/wiki/Virtual_image

    For a (reflecting) mirror, the real image is on the same side as the object while the virtual image is on the opposite side of, or "behind", the mirror. In diagrams of optical systems, virtual rays (forming virtual images) are conventionally represented by dotted lines, to contrast with the solid lines of real rays.

  8. Cardinal point (optics) - Wikipedia

    en.wikipedia.org/wiki/Cardinal_point_(optics)

    A system is focal if an object ray parallel to the axis is conjugate to an image ray that intersects the optical axis. The intersection of the image ray with the optical axis is the focal point F ′ in image space. Focal systems also have an axial object point F such that any ray through F is conjugate to an image ray parallel to the optical axis.

  9. Angle of incidence (optics) - Wikipedia

    en.wikipedia.org/wiki/Angle_of_incidence_(optics)

    The angle of incidence, in geometric optics, is the angle between a ray incident on a surface and the line perpendicular (at 90 degree angle) to the surface at the point of incidence, called the normal. The ray can be formed by any waves, such as optical, acoustic, microwave, and X-ray. In the figure below, the line representing a ray makes an ...