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| Question | Answer |
| What does Morse code use to represent letters of the alphabet? | Morse code uses a series of dots and dashes to represent letter of the alphabet. |
| Fill in the gaps: This code is used by signalling lamps as a series of short and long ....... .. ...... | This code is used by signalling lamps as a series of short and long flashes of light. |
| Finish the sentence: When a signal is sent by light, electricity, microwaves or radio, it is almost .............. | When a signal is sent by light, electricity, microwaves or radio, it is almost instantaneous. |
| Each method of transmission has advantages and disadvantages. Name what these could be. | - Can the signal be seen by others? - Can wires be cut? - How far does the signal have to travel? |
| What is white light made up of? | White light is made up of different colours of different frequencies out of phase. |
| Name the three features about laser light. | Laser light has only a single frequency, is in phase and has a low divergence. |
| Laser light is used to do what? | Laser light is used to read from the surface of a compact disc (CD). |
| How does this work? | - The surface of the CD is pitted - The pits represent the digital signal - Laser light is shone onto the CD surface and the difference in the reflection provides the information for the digital signal. |
| What normally happens when light travels from one material to another. | When light travels from one material to another, it is normally refracted. |
| If it is passing from a more dense material into a less dense material, is the angle of refraction larger or smaller than the angle of incidence? | If it is passing from a more dense material into a less dense material, the angle of refraction is larger than the angle of incidence. |
| Draw a labelled diagram to show what happens when light exits a glass block. |
Image:
refraction (image/jpg)
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| What is the angle of incidence called when the angle of refraction is 90°? | When the angle of refraction is 90°, the angle of incidence is called the critical angle. |
| Draw a labelled diagram to show what happens when the angle of incidence is at the critical angle. | |
| If the angle of incidence is bigger than the critical angle, the light is reflected. What is this called? | If the angle is bigger than the critical angle, the light is reflected. This is total internal reflection. |
| Draw a labelled diagram to show total internal reflection. | |
| What are telephone communications and computer data are transmitted long distances along? | Telephone communications and computer data are transmitted long distances along optical fibres. At the speed of light - 200000 km/s in glass |
| Fill the gaps: Some ...... are coated to improve ........... | Some fibres are coated to improve reflection. |
| What is an optical fibre? | An optical fibre is a flexible optically transparent fibre, usually made of glass or plastic, through which light passes by successive internal reflections. |
| What is an endoscope and what does it allow doctors to do? | An endoscope is a device using optical fibres which allows doctors to look inside the human body. |
| How does an endoscope work? | - Light passes along one set of optical fibres to illuminate the inside of the body. - The light is reflected. - The reflected light passes up another set of fibres to an eyepiece or camera. |
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