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  1. Light Reflection and Refraction. Light is a complex phenomena. It exhibits both wave * -like and particle-like properties. Its exact nature is not fully understood and this complexity makes it difficult for one model to describe all of light’s properties.

    • Overview
    • Reflection and refraction

    Light rays change direction when they reflect off a surface, move from one transparent medium into another, or travel through a medium whose composition is continuously changing. The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray. (By convention, all angles in geometrical optics are measured with respect to the normal to the surface—that is, to a line perpendicular to the surface.) The reflected ray is always in the plane defined by the incident ray and the normal to the surface. The law of reflection can be used to understand the images produced by plane and curved mirrors. Unlike mirrors, most natural surfaces are rough on the scale of the wavelength of light, and, as a consequence, parallel incident light rays are reflected in many different directions, or diffusely. Diffuse reflection is responsible for the ability to see most illuminated surfaces from any position—rays reach the eyes after reflecting off every portion of the surface.

    When light traveling in one transparent medium encounters a boundary with a second transparent medium (e.g., air and glass), a portion of the light is reflected and a portion is transmitted into the second medium. As the transmitted light moves into the second medium, it changes its direction of travel; that is, it is refracted. The law of refraction, also known as Snell’s law, describes the relationship between the angle of incidence (θ1) and the angle of refraction (θ2), measured with respect to the normal (“perpendicular line”) to the surface, in mathematical terms: n1 sin θ1 = n2 sin θ2, where n1 and n2 are the index of refraction of the first and second media, respectively. The index of refraction for any medium is a dimensionless constant equal to the ratio of the speed of light in a vacuum to its speed in that medium.

    By definition, the index of refraction for a vacuum is exactly 1. Because the speed of light in any transparent medium is always less than the speed of light in a vacuum, the indices of refraction of all media are greater than one, with indices for typical transparent materials between one and two. For example, the index of refraction of air at standard conditions is 1.0003, water is 1.33, and glass is about 1.5.

    The basic features of refraction are easily derived from Snell’s law. The amount of bending of a light ray as it crosses a boundary between two media is dictated by the difference in the two indices of refraction. When light passes into a denser medium, the ray is bent toward the normal. Conversely, light emerging obliquely from a denser medium is bent away from the normal. In the special case where the incident beam is perpendicular to the boundary (that is, equal to the normal), there is no change in the direction of the light as it enters the second medium.

    Light rays change direction when they reflect off a surface, move from one transparent medium into another, or travel through a medium whose composition is continuously changing. The law of reflection states that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray. (By convention, all angles in geometrical optics are measured with respect to the normal to the surface—that is, to a line perpendicular to the surface.) The reflected ray is always in the plane defined by the incident ray and the normal to the surface. The law of reflection can be used to understand the images produced by plane and curved mirrors. Unlike mirrors, most natural surfaces are rough on the scale of the wavelength of light, and, as a consequence, parallel incident light rays are reflected in many different directions, or diffusely. Diffuse reflection is responsible for the ability to see most illuminated surfaces from any position—rays reach the eyes after reflecting off every portion of the surface.

    When light traveling in one transparent medium encounters a boundary with a second transparent medium (e.g., air and glass), a portion of the light is reflected and a portion is transmitted into the second medium. As the transmitted light moves into the second medium, it changes its direction of travel; that is, it is refracted. The law of refraction, also known as Snell’s law, describes the relationship between the angle of incidence (θ1) and the angle of refraction (θ2), measured with respect to the normal (“perpendicular line”) to the surface, in mathematical terms: n1 sin θ1 = n2 sin θ2, where n1 and n2 are the index of refraction of the first and second media, respectively. The index of refraction for any medium is a dimensionless constant equal to the ratio of the speed of light in a vacuum to its speed in that medium.

    By definition, the index of refraction for a vacuum is exactly 1. Because the speed of light in any transparent medium is always less than the speed of light in a vacuum, the indices of refraction of all media are greater than one, with indices for typical transparent materials between one and two. For example, the index of refraction of air at standard conditions is 1.0003, water is 1.33, and glass is about 1.5.

    The basic features of refraction are easily derived from Snell’s law. The amount of bending of a light ray as it crosses a boundary between two media is dictated by the difference in the two indices of refraction. When light passes into a denser medium, the ray is bent toward the normal. Conversely, light emerging obliquely from a denser medium is bent away from the normal. In the special case where the incident beam is perpendicular to the boundary (that is, equal to the normal), there is no change in the direction of the light as it enters the second medium.

  2. The changing of a light ray’s direction (loosely called bending) when it passes through variations in matter is called refraction. Refraction is responsible for a tremendous range of optical phenomena, from the action of lenses to voice transmission through optical fibers.

  3. Jun 7, 2023 · When waves of light hit a smooth surface, such as a mirror, they reflect off of it. They also bend, or refract, when they move between environments of different densities, such as when light passes from air into and through a glass lens.

  4. Light waves are refracted as they enter the glass because they are slowed down. The spectrum is produced because different colours of light travel at different speeds in glass.

  5. The Mathematics of Lenses. If a piece of glass or other transparent material takes on the appropriate shape, it is possible that parallel incident rays would either converge to a point or appear to be diverging from a point. A piece of glass that has such a shape is referred to as a lens.

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  7. Nov 14, 2024 · News •. Scientists Discover Lasers Can Block Light And Cast a Shadow • Nov. 13, 2024, 6:42 PM ET (ScienceAlert) The basic element in geometrical optics is the light ray, a hypothetical construct that indicates the direction of the propagation of light at any point in space.

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