Term
| Energy Transformations required for mobile-mobile communication? |
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Definition
| Sound Waves - Electrical Impulses - Digitised - Radio waves to base station - Electrical impulses to switching station - Electrical impulses to switching station - Electrical impulses to base station - Radio waves to mobile - Sound waves through microphone |
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Term
| Describe 1- 2- and 3- Dimensional waves |
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Definition
1- Waves along a rope -> Confined to medium
2- Ripples in a flat pond -> moves outwards from point of disturbance
3- Hanging light -> waves move in all directions |
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Term
| Difference Between mechanical and electromagnetic waves? |
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Definition
| Mechanical waves need a medium for propagation, electromagnetic waves do not |
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Term
| Difference between transverse and longitudinal waves? |
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Definition
| Transverse waves vibrate the particles of the medium perpendicular to the direction of propagation. Longitudinal waves vibrate the particles in the same direction as propagation |
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Term
| What is the relationship between frequency, velocity and wavelength for a wave? |
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Definition
V = F X Lamba
Velocity = Frequency X Wavelength |
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Term
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Definition
| Vibrations / Oscillations of particles in a medium |
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Term
| How do compressions and rarefactions of sound waves relate to transverse waves used to represent them? |
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Definition
Compression= Crest
Rarefaction= Trough |
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Term
| What part of the representative transverse waves relate to volume and pitch of sound waves? |
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Definition
Pitch = Frequency
Volume = Amplitude |
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Term
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Definition
| A reflection of a sound wave. You can only hear a portion of the reflected wave, and it is not in phase with the original |
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Term
| What is the principle of superposition? |
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Definition
| Waves from separate sources interfering with each other. When this happens, the amplitude of the waves are altered. |
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Term
| Describe common features of electromagnetic waves |
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Definition
Electromagnetic waves do not require a medium for propgation.
They move through space at the speed of light - 3x10^8
They are made up of alternating electric and magnetic force fields and ninety degrees to one another. |
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Term
| Which electromagnetic wavebands does the atmosphere filter out? |
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Definition
| UV, X-rays, Gamma rays, Infra-red |
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Term
| Order the electromagnetic spectrum from longest wavelength to shortest |
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Definition
| Radio - Micro - Infra-red - Visible light - Ultraviolet - X - Gamma |
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Term
| What is the relationship between the intensity of electromagnetic radiation and the distance from the source? |
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Definition
The inverse square law.
I is proportional to 1/d^2 |
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Term
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Definition
| AM radio is an example of amplitude modulation. The amplitude of a carrier wave is varied by the broadcast, this is decoded by the receiver. AM has more static, but also more bandwidths available. |
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Term
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Definition
| FM radio is an example of frequency modulation. the signal part of the wave has been added to the carrier wave to vary the frequency of the wave. FM has less static, but also fewer bandwidths |
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Term
| What is the law of reflection? |
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Definition
| Angle of incidence = Angle of reflection. |
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Term
| How have light, radio and microwaves assisted in information transfer? |
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Definition
| Telescopes, torches/driving lights, satellite dishes, radio, phones. |
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Term
Describe one application of reflection for each of the following:
-Plane surfaces
-Concave surfaces
-Convex surfaces
-Radio waves & the ionosphere |
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Definition
-Plane surfaces: Mirrors
-Concave surfaces: Car lights, satelitte
-Convex surfaces: Safety mirrors
-Radio waves with high frequencies and short wavelengths are relfected off the earth and ionosphere |
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Term
| What is refraction and how does it work? |
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Definition
| Refraction is when waves that are incident on any angle except the normal bend as they pass from one medium or depth to another. The wavelength of the wave changes when the wave moves across an interface between mediums in which it has different velocities |
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Term
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Definition
V1/V2 = sin i/sin r = n2/n1 = wl1/wl2
(n= refractive index of medium) |
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Term
| Identify the conditions necessary for total internal reflection |
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Definition
| Total internal reflection occurs when a ray attempts to cross a medium at the critical angle and cannot escape. When the angle of incidence exceeds the critical angle, the interface will act as a mirror |
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Term
| How is total internal reflection used in optical fibres? |
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Definition
| Optical fibres have high refractive index glass as their core and lower 'n' as the cladding. Once light enters the core, it is totally internally reflected along the fibre, to transfer information at the speed of light. They are also flexible so can round corners without the use of mirrors |
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Term
| Identify types of communication data that are stored or transmitted in digital form. |
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Definition
| Optical fibres, mobile phones, television, inernet, cd's, dvd's, GPS |
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