IGCSE 0625 · EM SPECTRUM · 3.3

The electromagnetic spectrum

The whole electromagnetic family from radio to gamma: the shared properties, the ordered spectrum, what each region is used for, its harmful effects, and the Extended idea of digital versus analogue signals.

TOPIC 3.3: THE ELECTROMAGNETIC SPECTRUM CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com ALL EM WAVES SHARE A family of transverse waves that carry energy. They all travel at the same speed in a vacuum. They differ only in wavelength and frequency. KEY FACTS v = f λ links speed, frequency c = 3.0 × 10⁸ m/s speed in a vacuum THE SPECTRUM: LOW TO HIGH FREQUENCY wavelength increases frequency increases Radio > 1 m Microwave ~ 1 cm Infrared ~ 10 µm Visible ~ 500 nm Ultraviolet ~ 10 nm X-rays ~ 0.1 nm Gamma < 0.01 nm A handy order, low to high frequency: Radio, Microwave, Infrared, Visible, Ultraviolet, X-rays, Gamma. USES OF EACH REGION Radio TV and radio broadcasting Communications Microwave Satellite links Mobile phones, Wi-Fi Cooking food Infrared Remote controls Thermal imaging Heaters, fibre optics Visible Human vision Photography Illumination Ultraviolet Fluorescent lamps Security marking Sterilising, tanning X-rays Imaging bones Airport security Gamma Sterilising tools Treating cancer HARMFUL EFFECTS Higher-frequency waves carry more energy and do more damage to the body. Microwaves internal heating of body tissue Infrared skin burns Ultraviolet skin cancer, eye damage, ageing X-rays and gamma ionising: cell mutation and cancer DIGITAL vs ANALOGUE SIGNALS EXTENDED An analogue signal varies continuously. A digital signal is a stream of pulses, on or off (1 or 0). analogue digital Both pick up noise and weaken over distance. Digital noise is removed and the signal is regenerated cleanly by a regenerator. Digital carries more information at higher quality, and is easy to process, store, and encrypt.
TOPIC 3.3: THE ELECTROMAGNETIC SPECTRUM CAMBRIDGE IGCSE PHYSICS 0625 · PATHWAYS TheLucidSTEM · thelucidstem.com ALL EM WAVES SHARE A family of transverse waves that carry energy. They all travel at the same speed in a vacuum. They differ only in wavelength and frequency. KEY FACTS v = f λ links speed, frequency c = 3.0 × 10⁸ m/s speed in a vacuum THE SPECTRUM: LOW TO HIGH FREQUENCY wavelength increases frequency increases Radio > 1 m Microwave ~ 1 cm Infrared ~ 10 µm Visible ~ 500 nm Ultraviolet ~ 10 nm X-rays ~ 0.1 nm Gamma < 0.01 nm A handy order, low to high frequency: Radio, Microwave, Infrared, Visible, Ultraviolet, X-rays, Gamma. USES OF EACH REGION Radio TV and radio broadcasting Communications Microwave Satellite links Mobile phones, Wi-Fi Cooking food Infrared Remote controls Thermal imaging Heaters, fibre optics Visible Human vision Photography Illumination Ultraviolet Fluorescent lamps Security marking Sterilising, tanning X-rays Imaging bones Airport security Gamma Sterilising tools Treating cancer HARMFUL EFFECTS Higher-frequency waves carry more energy and do more damage to the body. Microwaves internal heating of body tissue Infrared skin burns Ultraviolet skin cancer, eye damage, ageing X-rays and gamma ionising: cell mutation and cancer DIGITAL vs ANALOGUE SIGNALS EXTENDED An analogue signal varies continuously. A digital signal is a stream of pulses, on or off (1 or 0). analogue digital Both pick up noise and weaken over distance. Digital noise is removed and the signal is regenerated cleanly by a regenerator. Digital carries more information at higher quality, and is easy to process, store, and encrypt.
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