Sunday, 24 January 2010
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Friday, 15 January 2010
So refractive index is measure of how much speed of light is reduced inside a medium such as glass etc:
The Refractive Index of Water
longer focal length or lower optical power is associated with larger magnification of distant objects
So that is why when the lens goes out more, there is greater magnification it is like Far sighted
Focal length is longer. for greater magnification. http://isleofmanmansions.blogspot.com/
For an optical system in air, it is the distance over which initially collimated rays are brought to a focus. A system with a shorter focal length has greater optical power than one with a long focal length; that is, it bends the rays more strongly, bringing them to a focus in a shorter distance.
Optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or diverges light. It is equal to the reciprocal of the focal length of the device. The dioptre is the most common unit of measurement of optical power. The SI unit for optical power is the inverse metre (m-1).
For two or more thin lenses close together, the optical power of the combined lenses is approximately equal to the sum of the optical powers of each lens. Similarly, the optical power of a single lens is roughly equal to the sum of the powers of each surface. These approximations are commonly used in ophthalmology.
When a lens is immersed in a medium, its optical power and focal length change.
An eye that has too much or too little refractive power to focus light onto the retina has a refractive error. A myopic eye has too much power so light is focused in front of the retina. Conversely, a hyperopic eye has too little power so when the eye is relaxed, light is focused behind the retina. An eye with a refractive power in one meridian that is different from the refractive power of the other meridians has astigmatism. Anisometropia is the condition in which one eye has a different refractive power than the other eye.
In optics, chromatic aberration (also called achromatism or chromatic distortion) is the failure of a lens to focus all colors to the same point. It occurs because lenses have a different refractive index for different wavelengths of light (the dispersion of the lens). The refractive index decreases with increasing wavelength.
Chromatic aberration manifests itself as "fringes" of color along boundaries that separate dark and bright parts of the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.
Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both longitudinal, in that different wavelengths are focused at a different distance from the lens; and transverse or lateral, in that different wavelengths are focused at different positions in the focal plane (because the magnification of the lens also varies with wavelength).
Thursday, 14 January 2010
isle of man mansions
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