Optical fibres are used to transmit digital signals using infrared radiation. The average refractive index of the fibres is 1.60.
Which row in the table below correctly describes a digital signal and gives the speed of this infrared radiation in the fibres (taking the speed of light in vacuum to be c=3.0×108 m/sc = 3.0 \times 10^8 \text{ m/s}c=3.0×108 m/s)?
| Description of a digital signal | Speed of infrared radiation in the fibres (m/s\text{m/s}m/s) | |
|---|---|---|
| A | A signal consisting of only two values | 1.9 × 108 |
| B | A signal consisting of only two values | 4.8 × 108 |
| C | A signal consisting of a continuously varying range of values | 1.9 × 108 |
| D | A signal consisting of a continuously varying range of values | 4.8 × 108 |
Row A
Row B
Row C
Row D
216 exam-style questions on CIE IGCSE Physics 3.2 Light, covering 3.2.1a Reflection of light, 3.2.1b Images in a plane mirror, 3.2.2 Refraction of light, 3.2.2a Refraction of light, 3.2.2b Total internal reflection, 3.2.2c Refractive index and critical angle, 3.2.2d Optical fibres, 3.2.3a Converging and diverging lenses, 3.2.3b Ray diagrams and the nature of images, 3.2.3c Virtual images and the magnifying glass, 3.2.3d Correcting long-sightedness and short-sightedness, and 3.2.4 Dispersion of light. Each one has a worked solution and a mark scheme showing where the marks go.