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13 Cards in this Set
- Front
- Back
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Optical fibre |
Is a long thin strand made of (quality glass/ quartz) surrounded by a coating if slightly lower refractive index. |
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Applications of optical fibre |
Generally Used as a guided medium for transmitting an optical signal from one place to another. •As a light pipe; used in medical and optical examination •transmitting and recieving electrical signals in telecommunication . •transmitting optical signals and 2d pictures • In the form of refractometers, they're used to measure refractive indices of liquids. |
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Mirage definition |
Definition: it is an optical illusion (in deserts or overhot extended surfaces,) due to which a traveller sees a shimmering pond of water some distance ahead of him and in which the surrounding objects appear inverted. |
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Applications of TIR |
•mirage •sparkling/brilliancy of diamond(RI of diamond is very large, this it's critical angle is very small. Faces of diamond are so cut that the light entering the crystals suffers TIR's repeatedly (and hence gets collected inside but comes out through only a few faces) •totally reflecting prisms •optical fibres |
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What is total internal reflection. Give the two conditions. Relation between refractive index and critical angle |
Total internal reflection: the phenomenon in which ray of lighter travelling from a denser to rarer medium is totally reflected back into the denser medium. |
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Critical angle |
The angle of incidence in a denser medium for which the angle of refraction is 90°. Denoted be Ic |
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Necessary conditions for TIR |
• Light must travel from optically denser to optically rarer medium. •angle of incidence in denser medium must be greater than critical angle for the two media. |
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Working of optical fibre |
Optical fibre consists of an outer cladding (made of glass/plastic jacket) and inner core (also made of glass/silica/plastic) whose refractive index is greater than that of cladding . The core and cladding are so chosen that the critical angle for the two media is small Propagation: when light is incident on one end of the fibre at a small angle, it goes inside and suffers repeated TIR's because the angle of incidence is greater than critical angle of the fibre wrt outer coating. The light finally emerges with undiminished intensity at the other end. Even if the fibre is bent, this process is not affected. |
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Relationship between critical angle and (relative) refractive index for the two media |
Ur= refractive index of rarer medium Ud= RI of denser medium As angle of incidence increases angle of refraction also increases. |
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Mirror Formula |
1/f= 1/v +1/u |
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Lens formula (aka thin lens formula) |
1/f= 1/v -1/u |
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SRF |
Valid for single surfaces only (single refraction) |
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Lens makers formula |
Gives the relation between focal length of the lens and the radius of curvature of its two surfaces. (Tip for derivation of lens makers formula: you don't need to use the sign conventions while deriving it ) |
