Y9 Physics - Uses of non ionising EM Waves

-non ionising electromagnetic waves (EM waves with … to remove … from atoms)

EM waves with too little energy to remove electrons from atoms

Non-ionising parts of the EM spectrum

radio waves, microwaves, infrared, visible light,

Speed of all EM waves in air/vacuum

3.0 × 10⁸ m/s (speed of light)

What all EM waves transfer (2)

energy and information

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📻 Radio waves

Radio waves (definition)

lowest frequency and longest wavelength EM waves

Uses of radio waves (5)

TV broadcasting, radio broadcasting, mobile phones, Wi-Fi, Bluetooth

How radio waves are produced (6 words)

oscillating electrical charges in a transmitting antenna

How radio waves are detected

absorbed by a receiving antenna causing charges to oscillate

Why radio waves are good for long-distance communication (… well through…, … around …, some … off the …)

transmit well through air and buildings, diffract around hills, some reflect off the ionosphere

Danger of radio waves (…body… …intensities)

heating of body tissue at very high intensities

Microwaves (definition)

EM waves with higher frequency and shorter wavelength than radio waves

Uses of microwaves

cooking food, satellite communication, mobile phone networks, Wi-Fi

Why microwaves are good for satellite communication

pass through the atmosphere, travel in straight lines, can be aimed accurately at satellites

Why microwaves are good for cooking

water absorbs microwaves, water molecules gain energy and rotate, heating the food

Why microwaves do not escape from ovens

metal sides and metal mesh reflect microwaves back inside

Danger of microwaves

internal heating of body tissue at high intensity

Infrared (definition)

EM waves with longer wavelength and lower frequency than visible light

Source of infrared radiation

all objects emit IR, hotter objects emit more

Uses of infrared

heaters, remote controls, thermal cameras, short-range data links

How thermal imaging cameras work

detect and absorb IR intensity, convert it to temperature, display it as colours

Danger of infrared(…to skin and … to … at …)

burns to skin and damage to eyes at high intensity

Visible light (definition)

EM radiation that can be detected by the human eye

Position of visible light in spectrum

between infrared and ultraviolet

Uses of visible light (4)

seeing, photography, lighting, fibre-optic communication

Why visible light is good for fibre optics (total …, very little …, thin and …)

total internal reflection, very little signal loss, thin and secure fibres

Danger of visible light (…or temporary bli…light)

eye damage or temporary blindness from very bright light

What is total internal reflection (When …boundary…less dense medium…fully…medium)

When light hits a boundary with a less dense medium and reflects fully into the denser medium