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24 Cards in this Set
- Front
- Back
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What’s a lens |
It’s a transparent object with at least one curved surface. Lenses control the direction of light rays passing through them by having an index of refraction greater than the index of refraction of air |
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What are the type of lenses? |
Converging lenses and diverging lenses |
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True or false? In a lens, light undergoes refraction twice (similar to a prism) |
True |
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What’s optical centre? |
Geometric center of lens |
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What’s a Principal focal point |
Where rays parallel to P converge (real) |
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What’s the secondary focal point |
Point of symmetrical to principal focal point in relation to (O). On side of incident rays |
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What’s a focal length |
The distance OF (F) |
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In a converging lenses whats the first principal ray? |
Incident ray parallel to P refracted towards F |
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In converging lenses, what’s the second principal ray |
The incident ray passes through F prime, refracted rays are parallel |
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In a converging lenses, where does the third principal ray pass through? |
It passes through O, no deviation |
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In a Diverging lenses, where does the first principal ray pass through |
Incident ray parallel to P, refracted so it appears to come From F |
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In a diverging lenses, where does the second principal ray go through? |
Incident ray points towards F prime, refracted parallel |
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In a diverging lenses, where does the third principal ray go through? |
It passes through O, no deviation |
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What are the characteristics of the image in a converging lenses |
Real or virtual Smaller or larger or same Inverted or upright Location in relation to F and 2F |
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True or false? Images formed by diverging lenses are ALWAYS: virtual, upright, smaller than the object and smaller than F (on the side of the object between the object and the lens) |
True |
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When the focal length is positive that means… |
It’s a converging lens |
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When a focal length is negative that means…. |
Diverging lens |
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What is optical power? |
It’s a measure that quantifies the capacity of a lens to deviate light rays. The more an optical system is able to converge or diverge light rays, the greater the optical power will be. Smaller the focal length, the greater optical power |
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Optical power formula (dioptres) |
P= 1/f (Focal length has to be in meters) |
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Formula to remember when there are many lenses placed side by side |
Pt= P1 + P2 +……. Pn Also same as 1/ft= 1/f1 + 1/f2 +….. 1/fn Pt= 1/fT |
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What are the visual disorders and their corrections? |
Myopia (diverging), Eye too long or cornea or lens too curved P (optical power) is too high Hyperopia (converging), images behind retina, optical power is too small. With lens P is increased |
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What’s astigmatism? |
Irregularities of cornea |
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What’s presbyopia |
Loss of elasticity |
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Difficulty reading the blackboard from the back of the class as well as seeing details of a movie from the back of the theatre is called what |
Nearsightedness |
