Problem area (7) Flashcards
What are the types of waves in the electromagnetic spectrum?
Radio waves, microwaves (sometimes), infared, light, ultraviolet, X-rays, gamma rays
What are the rough frequencies and wavelengths of radio waves?
Frequency: 10^5 - 10^10 Hz; wavelength: 10^4 - 10^(-2)m
What are the rough frequencies and wavelengths of microwaves?
Frequency: 10^10 Hz; wavelength: 10^(-2)m
What are the rough frequencies and wavelengths of infared?
Frequency: 10^12 - 10^14 Hz; wavelength: 10^(-3) - 10^(-6)m
What are the rough frequencies and wavelengths of ultraviolet?
Frequency: 10^15 - 10^17 Hz; wavelength: 10^(-7) - 10^(-9)m
What are the rough frequencies and wavelengths of X-rays?
Frequency: 10^18 - 10^19 Hz; wavelength: 10^(-9) - 10^(-11)m
What are the rough frequencies and wavelengths of gamma rays?
Frequency: 10^20 - 10^22 Hz; wavelength: 10^(-11) - 10^(-14)m
What are the types of radio waves?
Long waves, medium waves, short waves, very high frequency (VHF) waves, ultra high frequency (UHF) waves, microwaves
How are radio waves produced? (naturally)
Stars naturally emit radio waves
How are radio waves produced? (artificially)
A current oscillates in a transmitting aerial (antenna) producing radio waves. A microphone can control the current to the aerial so the radio waves “pulsate”
How are radio waves received to produce a sound?
In the radio receiver, incoming pulsations control a loudspeaker so it produces a copy of the original sound (pulsations turn to current)
What are long wave radio waves used for?
Long-distance AM radio
What are medium wave radio waves used for?
Local AM radio
What are short wave radio waves used for?
Amateur radio
What are very high frequency (VHF) waves used for?
FM radio
What are ultra high frequency (UHF) waves used for?
TV broadcasts
What radio waves can diffract around hills?
Long and medium waves
What are microwaves used for?
Mobile phones, TV and communications, satellites, telephone links, Wi-Fi, radar, heating effect used in microwave ovens
What is a danger of microwaves?
They can cause internal heating of body tissues if the body is exposed to them
What type of radiation do all objects emit?
Infrared radiation
At what temperatures do objects glow “red hot” and “white hot”?
At about 700°C, red hot; above about 1000°C, white hot
What is infrared radiation used for?
Radiant heaters and grills; TV remote controllers; security alarms and lamps; “light” pulses in optical fibres
What is visual light used for?
Seeing things with the eye
What does ultraviolet radiation do?
Causes tanning; skin cancer; eye damage; causes fluorescence (makes some chemicals glow); kills bacteria
