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Light Reflection and Refraction
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24/08/2021 12:49 pm
Topic starter
The optical prescription for a pair of spectacles is:
Right eye: –3.50 D Left eye : –4.00 D
(a) Are these lenses thinner at the middle or at the edges?
(b) Which lens has a greater focal length?
(c) Which is the weaker eye?
1 Answer
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24/08/2021 12:50 pm
(a) These lenses have negative powers and hence negative focal lengths, so they are concave lenses.
Concave lenses are thinner in the middle.
(b) Lens of lower power has greater focal length. So, -3.50 D lens has greater focal length.
(c) Left eye is the weaker one because it needs a lens of greater power for its correction.