Light Purple
Light Purple
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 Light Purple Case Aluminum Cover Shell for Sony PSP GO  US $5.76
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 XBOX 360 Ring of Light MOD KIT ROL 5 PURPLE LED US $4.99
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 Light Purple Protective Aluminum Shell for Sony PSP GO US $7.67
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 50 PURPLE LED RING OF LIGHT MOD XBOX 360 CONTROLLER ROL US $22.99
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 Light Purple Full Housing For Nintendo DS Lite NDSL US US $13.26
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 100 PURPLE LED RING OF LIGHT MOD XBOX 360 CONTROLLER ROL US $39.99
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 6/5/3 Mode (modes) Rapid Fire Controller or Service US $62.00
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6/5/3 Mode (modes) Rapid Fire Controller or Service US $61.00
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6/5/3 Mode (modes) Rapid Fire Controller or Service US $65.00
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6/5/3 Mode (modes) Rapid Fire Controller or Service US $65.00
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6/5/3 Mode (modes) Rapid Fire Controller or Service US $25.00
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 Light Purple ALUMINUM COVER HARD CASE FOR SONY PSP 2000 US $4.40
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 Light Purple Protective Aluminum Shell for Sony PSP GO US $5.76
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 Light Purple Protective Aluminum Shell for Sony PSP GO US $7.67
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 WORM LIGHT GAME BOY COLOR GBC WORMLIGHT PURPLE *NEW* US $.99
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 Xbox 360 Modded Controller | Rapid Fire | Purple LED Lights! | Good Price US $.99
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Which would have a longer focal length when passed though a convex lens? Red or Purple light?
Im having a little trouble understanding this or finding useful information on the internet. Basically I need to find out the focal length of a convex lens when red light is passed through it, and when purple light is passed through it. I know that purple light is faster and more energetic that red light. So will be less affected by the refracted properties of a convex lens? And will it travel less or more that red light in terms of focal length?
Purple will focus in front of red light for a 'thick' convex lens. This effect is called ‘chromatic aberration’. It is an easy matter to observe chromatic aberration. If a candle is used as the object, a converging lens will cast a real image surrounded by a halo. If the plane of observation is then moved nearer to the lens, the periphery of the blurred image will become tinged orange-red. Moving it back away from the lens, beyond the best image, will cause the outline to become tinted in blue-violet! The location of the 'circle of least confusion' corresponds to the position where the best image will appear.
Chromatic aberration occurs with polychromatic light because the refraction of light by a medium of different refractive index 'ni' (Snell's law) is wavelength dependent. From the thin lens equation: -
1 = (ni - 1) | 1 - 1 .|
_ ............ | _ .. _ |
f ............. | R1 R2|
Where 'f' is the focal length of the lens and 'R1, R2' are its two radii of curvature. Since, the value of the refractive index 'ni' of the lens is light wavelength dependent, then so too must be the focal length 'f' of the lens. Hence, the focal length of the lens increases with increasing light wavelength. Thus, blue-violet light, with a shorter wavelength, focuses slightly in front of red-orange light.
After some limited experiments, Isaac Newton gave up trying to remove chromatic aberration from refracting telescope lenses and produced the first reflecting telescope in 1688. Newton erroneously concluded that the removal of chromatic aberration from a lens was impossible.
Chromatic aberration may be removed from lenses using thin achromatic doublet lenses (one positive and the other negative) of different refractive indexes so that ‘f(red)’ overlaps ‘f(blue)’.