Geometric optics describes the interaction of light with macroscopic objects. Why, then, is it correct to use geometric optics to analyse a microscope’s image?
We use geometric optics approximation because the size of the object is much larger than the wavelength of light.
One approximation that geometric optics makes is that the waves (rays) travel in straight lines until they hit a surface. When the ray encounters a surface it can either bounce back (reflect) or bend (refract) but then continues to travel in a straight line.
The size of the object we see in the microscope is of the order of . The wavelength of the light used in the microscope is of the order of few 100 nm . So the wavelength of the light is much smaller than the size of the object, hence we can use the geometrical optics approximation.
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?
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?
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