# Shared Flashcard Set

## Details

The World Communicates
BOS Preliminary Physics, Topic 1 Revision
24
Physics
05/17/2014

Term
 Energy Transformations required for mobile-mobile communication?
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
Term
 Describe 1- 2- and 3- Dimensional waves
Definition
 1- Waves along a rope -> Confined to medium2- Ripples in a flat pond -> moves outwards from point of disturbance3- Hanging light -> waves move in all directions
Term
 Difference Between mechanical and electromagnetic waves?
Definition
 Mechanical waves need a medium for propagation, electromagnetic waves do not
Term
 Difference between transverse and longitudinal waves?
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
Term
 What is the relationship between frequency, velocity and wavelength for a wave?
Definition
 V = F X LambaVelocity = Frequency X Wavelength
Term
 What are sound waves?
Definition
 Vibrations / Oscillations of particles in a medium
Term
 How do compressions and rarefactions of sound waves relate to transverse waves used to represent them?
Definition
 Compression= CrestRarefaction= Trough
Term
 What part of the representative transverse waves relate to volume and pitch of sound waves?
Definition
 Pitch = Frequency Volume = Amplitude
Term
 What is an echo?
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
Term
 What is the principle of superposition?
Definition
 Waves from separate sources interfering with each other. When this happens, the amplitude of the waves are altered.
Term
 Describe common features of electromagnetic waves
Definition
 Electromagnetic waves do not require a medium for propgation.They move through space at the speed of light - 3x10^8They are made up of alternating electric and magnetic force fields and ninety degrees to one another.
Term
 Which electromagnetic wavebands does the atmosphere filter out?
Definition
 UV, X-rays, Gamma rays, Infra-red
Term
 Order the electromagnetic spectrum from longest wavelength to shortest
Definition
 Radio - Micro - Infra-red - Visible light - Ultraviolet - X - Gamma
Term
 What is the relationship between the intensity of electromagnetic radiation and the distance from the source?
Definition
 The inverse square law.I is proportional to 1/d^2
Term
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.
Term
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
Term
 What is the law of reflection?
Definition
 Angle of incidence = Angle of reflection.
Term
 How have light, radio and microwaves assisted in information transfer?
Definition
 Telescopes, torches/driving lights, satellite dishes, radio, phones.
Term
 Describe one application of reflection for each of the following:-Plane surfaces-Concave surfaces-Convex surfaces-Radio waves & the ionosphere
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
Term
 What is refraction and how does it work?
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
Term
 What is Snell's Law?
Definition
 V1/V2 = sin i/sin r = n2/n1 = wl1/wl2(n= refractive index of medium)
Term
 Identify the conditions necessary for total internal reflection
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
Term
 How is total internal reflection used in optical fibres?
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
Term
 Identify types of communication data that are stored or transmitted in digital form.
Definition
 Optical fibres, mobile phones, television, inernet, cd's, dvd's, GPS
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