A pure red object on a black background seems to disappear when illuminated with pure green light. Explain why.
A pure red object absorbs all the green light and forms black color and due to the black background, it seems to have disappeared.
To explain, the concept of the "true color" of an object is applied. When any object reflects the light falling on it, then the color corresponding to the wavelength of reflected light is known as the true color of the object.
In another sense, the true color of an object is defined by its absorptive and reflective characteristics of the surface, where the light falls and gets reflected. And it is also related to the relative absorption of various wavelengths of light.
Now, when a pure red object is illuminated with pure green light, the object appears to be black. This happens because the object absorbs all the green light falling on it. As the background is also black, the object now seems to disappear.
Therefore, due to the red object absorbing green light, it appears to be disappeared.
It has become common to replace the cataract-clouded lens of the eye with an internal lens. This intraocular lens can be chosen so that the person has perfect distant vision. Will the person be able to read without glasses? If the person was near-sighted, is the power of the intraocular lens greater or less than the removed lens?
Unless otherwise stated, the lens-to-retina distance is 2.00 cm.
(a) A laser vision correction reshaping the cornea of a myopic patient reduces the power of his eye by 9.00 D, with a uncertainty in the final correction. What is the range of dioptres for spectacle lenses that this person might need after LASIK procedure? (b) Was the person near-sighted or farsighted before the procedure? How do you know?
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