Optical fibres typically include a transparent core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by the phenomenon of total internal reflection which causes the fibre to act as a waveguide.
Fibres that support many propagation paths or transverse modes are called multi-mode fibres, while those that support a single mode are called single-mode fibres.
Multi-mode fibres generally have a wider core diameter and are used for short-distance communication links and for applications where high power must be transmitted.
Section-1: General Science - Physics Question - 17
The unit usually used in professional astrometry is:
Superconductors are also able to maintain a current with no applied voltage whatsoever, a property exploited in superconducting electromagnets such as those found in MRI machines.
Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years.
Section-1: General Science - Physics Question - 20