electromagnetic waves

State order of electromagnetic waves going from long to short wavelength

radio, microwave, infrared, visible light (red to violet), ultraviolet, X-rays and gamma rays.

What type of waves are all electromagnetic waves

Transverse- oscillate perpendicular to the direction of energy transfer

What speed do all electromagnetic waves travel as through a vacuum or air

3×10^8m/s

What part of the spectrum can our eyes only detect

Visible light

Where can gamma rays be found

During radioactive decay

Where does visible light, UV and x rays come from

When electrons drop down energy levels

What waves can be used in communication

Radio and microwaves

Which waves are considered ionising

X rays and gamma rays

Radio waves

Longest wavelength and lowest frequency

How can we produce radio waves

Using electricity in the form of alternating current as AC are made up oscillating charges

What determines the frequency of the wave we are going to produce

Frequency of alternating current

What equipment is needed to generate radio waves

Oscilloscope-see the freq if AC

transmitter

Receiver-absorbs energy and generates AC on another oscilloscope which has the exact same frequency on first oscilloscope

Types of waves for radio wave communication

Long wave-huge distances and bend around the curved surface of earth

Short wave-long distances but can’t be curved instead reflected

Very short waves-TV and FM radio so have to be transmitted directly, not always clear

Two groups of microwaves

1)aren’t absorbed by water molecules I.e for satellites

2)absorbed by water molecules I.e microwave ovens

Infrared radiation

Emitted by all object that have thermal energy

Hotter the object=more IR radiation

IR cameras

Infrared radiation camera-see in dark

Can spot living organisms as they will lighter as emit more radiation

Cooking with IR

Oven and grills-metal emits lots of IR radiation which heats our food and heats our food by transferring the heat energy

Doesn’t penetrate the surface of food

Electric heaters with IR

Use electrical energy to heat metal which heats up surrounding I.e in our rooms

Visible light

Appears different colours depending on wave length

Red=longest wavelength

Violet=shortest wavelength

ROYGBIV

How is visible light used for communication

Using optical fibres that are thin glass or plastic fibres that can transmit pulses of light over long distances as light is reflected every time it hits a surface

Transmits data really quickly over long distances

Must have specular reflection

Ultraviolet uses

From sun or sun beds for tan or burns

Fluorescence=ultraviolet is absorbed and energy is re emitted as visible light

Security pens-detect writing when shone

Sterilise water

X rays main use

View internal structure of object I.e our body’s

Firing x-rays through body where rays are absorbed by bones but pass through parts that are mostly air I.e lungs and partially pass through fleshy parts

Dense areas=white like bones

Detect broken bones

Low dose so not too harmful and cheap and quick test

What is radiation measured in

Sieverts

Gamma rays for sterilisation

Medical equipment and food-kill microorganisms without causing other damage

Pros and cons of using gamma, X-rays in medicine

-both ionising radiation so can damage cells and potentially lead to cancer

-but help us to diagnose and treat diseases so worth the risk