electromagnetic spectrum

name two properties of all electromagnetic waves

all transverse waves

travel at the same speed (3×10⁸ m/s) through free space (a vacuum)

list the EM spectrum in order of wavelength, starting with the longest

radio waves, microwaves, infrared, visible light (ROYGBIV), ultra-violet, x-rays, gamma rays

what is the correlation between wavelength and frequency with EM waves?

the longer the wavelength, the lower the frequency

which EM wave has the highest frequency?

gamma rays

which part of the EM spectrum can humans see?

visible light (red - 700nm to blue - 350nm)

write out the colours of visible light in order of wavelength, starting with the longest

red, orange, yellow, green, blue, indigo, violet

what property do UV, x-rays and gamma rays share?

ionising

what property do radio waves and microwaves share?

used for communication

all EM waves can be … , … and …

reflected, refracted and difracted

uses of radiowaves

communication

television

radio

talking

dangers of radio waves

not thought to be dangerous

other cool stuff we need to know about radio waves

wavelengths longer than 10cm

produced by moving electrons

can easily bend around objects

uses of microwaves

radar, cooking, satellite communications, mobile phones

dangers of microwaves

increase vibrations of particles → internal heating in human body tissue

other cool stuff we need to know about microwaves

wavelength approx 1-10cm

need shielding to prevent from reaching users

uses of infrared

night vision, heat used in toasters/grills, remote controls, thermal imaging

dangers of infrared

heating effect

can cause burns

other cool things we need to know about infrared

IR is given out by all objects

hotter objects give out more IR

uses of visible light

photography, communication, medicine (optical fibres)

how do optical fibres work?

by bouncing waves off the sides of a very narrow core

dangers of visible light

eye strain, skin aging and disruption to sleep

uses of ultraviolet (UV)

fluorescent lamps (tanning lamps) - more energy efficient

sterilisation

check forgeries/security

dangers of UV

damage surface cells (skin burns)

cause blindness

can cause cancer

how do fluorescent lights work?

use UV radiation to emit visible light

uses of x-rays

view internal structures (medicine)

x-ray photography

x-ray crystallography (molecular structure of crystals)

dangers of x-rays

can cause mutations that lead to cancer

what are x-rays produced by?

moving electrons

how do they make an x-ray image?

x-rays directed through object/body through director plate

the bright bits are where few x-rays get through

uses of gamma rays

sterilisation (medical equipment and food)

radiotherapy

thickness testing

leak detection

dangers of gamma rays

ionising → cell death → cancer

where are gamma rays emitted from?

nucleus