Advertisements
Advertisements
Question
Write a note on optical fibre.
Solution
- Transmitting signals through optical fibres is possible due to the phenomenon of total internal reflection.
- Optical fibres consists of the inner part called core and an outer part called cladding (or) sleeving.
- The refractive index of the material of the core must be higher than that of the cladding for total internal reflection to happen.
- Signal in the form of light is made to an incident inside the core-cladding boundary at an angle greater than the critical angle.
- Hence, it undergoes repeated total internal reflections along the length of the fibre without undergoing any refraction.
APPEARS IN
RELATED QUESTIONS
Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20 cm?
A small pin fixed on a table top is viewed from above from a distance of 50 cm. By what distance would the pin appear to be raised if it is viewed from the same point through a 15 cm thick glass slab held parallel to the table? Refractive index of glass = 1.5. Does the answer depend on the location of the slab?
Does the apparent depth of a tank of water change if viewed obliquely? If so, does the apparent depth increase or decrease?
A narrow beam of light passes through a slab obliquely and is then received by an eye following figure. The index of refraction of the material in the slab fluctuates slowly with time. How will it appear to the eye? The twinkling of stars has a similar explanation.
What is mirage?
What is Snell’s window?
An object is immersed in a fluid of refractive index 'µ'. In order that the object becomes invisible when observed from outside, it should ______.
A concave mirror of focal length 'f1' is placed at a distance 'd' from a convex lens of focal length 'f2'. A parallel beam of light coming from infinity parallel to principal axis falls on the convex lens and then after refraction falls on the concave mirror. If it is to retrace the path, the distance 'd' should be ______.
The optical density of turpentine is higher than that of water while its mass density is lower. Figure shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in figure, the path shown is correct?
Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough the object looks distorted because ______.
- the apparent depth of the points close to the edge are nearer the surface of the water compared to the points away from the edge.
- the angle subtended by the image of the object at the eye is smaller than the actual angle subtended by the object in air.
- some of the points of the object far away from the edge may not be visible because of total internal reflection.
- water in a trough acts as a lens and magnifies the object.
