Electromagnetic Spectrum - HSphysics-chiakp

Urbain et civil

16 nov. 2013 (il y a 5 années et 5 mois)

114 vue(s)

ELECTROMAGNETIC
SPECTRUM

Name: ________________

Class: _________________

Index: ________________

At the end of the topic you should be able to…

state that all electromagnetic waves are transverse waves that
travel with the same high speed in vacuo and state the
magnitude of this speed

describe the main components of the electromagnetic spectrum

discuss the role of the following components in the stated
applications:

1.

2.
microwaves in satellite television and microwave oven

3.
infra
-
red waves in infra
-
red remote controllers and
intruder alarms

4.
light in optical fibres for medical uses and
telecommunications

5.
ultra
-
violet in sunbeds, and sterilisation

6.
X
-
rays in radiological and engineering applications

7.
Gamma rays in medical treatment

describe the effects of absorbing electromagnetic waves, e.g.
heating, ionisation and damage to living cells and tissue

Electromagnetic Spectrum

Properties

An electromagnetic wave is produced by the
simultaneous vibration of electric and magnetic
fields.

All electromagnetic waves

transfer energy from one place to another

are transverse waves

can travel through vacuum. They DO NOT
require any medium to travel from one point to
another.

travel through a vacuum at the speed of
3
x
10
8

ms
-
1
.

obey wave properties like reflection and
refraction.

carry no electrical charge as they are neither
positively nor negatively charged.

obey the wave equation: v = f

.

If electromagnetic waves travel in vacuum, then for the
wave equation

v =
f

v =
c
,

where c is the symbol for the speed of light in vacuum

c

=
f

3.0 x 10
8

=
f

Their frequencies do not change when they travel from
one medium to another.

(e.g.. From water to glass). This
is because their frequency ƒ depends only on the source
of the wave. Only their speeds and wavelengths change
from one medium to another.

Components of electromagnetic spectrum

Speed in a vacuum

is constant

c =
3
x
10
8

m s
-
1

Electromagnetic Spectrum

Gamma
rays

X
-
rays

Ultraviolet

Visible
light

Infrared

Microwave

wave

low
frequency

high
frequency

short
wavelength

long
wavelength

Several
km

<
10
-
12
m

Electromagnetic spectrum

“Ronald McDonald Is Very Ugly eXcept Gary”

For each component, you need to know

Range of wavelength

Its uses

Any harmful effects (The higher the frequency,
the larger the amount of energy)

Source

Detector

Applications of electromagnetic spectrum

has wavelength of 10
-
1

to 10
5

m

Can move around obstacles

is used in radio communication and television transmission
over long distances (LW, MW, SW, VHF, UHF). Radio
telescope.

with the use of VHF and UHF radio waves

detector: aerials of TV and radio

Microwave

has wavelength of
10
-
3

to
10
-
1

m (
0.001
m to
0.1
m)

is used in satellite communication and transmission, radar
systems and microwave cooking/microwave oven

travels in straight line without losing much of its energy

source: electronic devices
(eg. cavity magnetron in
microwaves)

detector: microwave

speed
-
monitoring

satellite station

is the radiation beyond the red end of the visible
spectrum

has wavelength of
10
-
7

to
10
-
3

m

is used in remote control devices, intruder alarms, infra
-

is emitted by hot objects

source: warm bodies

detector: special photographic films,
blackened thermometers and
thermocouples

an infra
-
red photograph

Visible light

can be seen by human eye

has wavelength of 4 x 10
-
7

to 7 x 10
-
7

m

is used in optical fibres, medical
usage, telecommunications,
chemical spectral analysis and
photosynthesis, endoscopy.
Lasers for medical, industrial and
surveying use.

source: hot bodies, lasers and sun

detector: eyes, photographic film
and photocells

laser surgery

has wavelength of
10
-
8

to
10
-
7

m

stimulates our bodies to produce vitamin D

Can cause tanning, overexposure can lead to skin cancer

is used in sunbeds, fluorescent tubes,
sterilisation, forgery detection and
fluorescence in washing powders

source: sun, mercury vapour and
lamps

detector: photographic film,
fluorescent screens, dyes and
photocells

cause skin cancer

X ray

has wavelength of 10
-
13

to 10
-
8

m

is penetrating and can cause damage to tissues
and organisms

Doctors, nurses and people working in X
-
ray
environment have to wear protective clothing
to shield themselves from X ray

is used in medical and dental diagnostic tools
and engineering applications. Check for
flaws/cracks in metals. Detect artwork forgery.
Airport scanners. Crystal structure analysis.

source: x
-
ray tubes

detector: photographic film and fluorescent
screens

x
-
ray photograph of hand

Gamma ray (HIGHEST ENERGY!!!!,
HIGHEST FREQUENCY)

has wavelength of 10
-
14

to 10
-
10

m

is penetrating and can cause damage to living tissues and
organisms

is used in treatment of cancer (gamma knives

sharp beam of
gamma ray) and checking of welds, under controlled situations.
Sterilising equipment.

source: cosmic rays, radioactive substances and nuclear reaction

detector: Geiger
-
Müller counters (GM tube), bubble/cloud
chambers and photographic film

Effects of EM Waves on Cells and Tissue

Exposure to electromagnetic radiation primarily causes heating effects
such as the pain of sunburn or skin cancer. However, over
-
exposure
may result in harmful effects such as pain of sunburn or skin cancer.

EM waves can be classified as either ionising radiation or non
-
ionising

Ionising radiations are extremely high frequency EM waves which
include X
-
rays and gamma rays. They have enough photon energy to
produce ionisation (a process where one or more electrons are
removed from a neutral atom by radiation). It is a harmful process
leading to destruction or modification of living cells.

Non
-
ionising radiations are the part of the EM spectrum which has
photon energies too weak to produce ionisation. Examples are ultra
-
violet, visible light, infra
-

Memory aid (song) for Electromagnetic Spectrum

3
D
4
Y

Electromagnetic
waves

c = 3 x 10
8
m s
-
1

Transverse
waves

are

with speed in
vacuum

Components

Microwaves

Infra
-
red
waves
.

Light

Ultra
-
violet
.

X
-
rays

Gamma rays

Applications

communication

Satellite television and
telephone

Home electrical appliances,
remote controls and intruder
alarms

Optical fibres in medical usage
and telecommuncation

Sunbeds, fluorescent tubes and
sterilisation

Medical use and engineering
applications

Medical treatment

consist of

Reference:

http://blogs.edf.org/climate411/2007/07/25/greenhouse_effect/

-
dishnetwork
-
cable.html

http://www.smh.com.au/news/technology/police
-
grapple
-
with
-
defective
-
detectors/2008/07/22/1216492432489.html

http://www.teara.govt.nz/en/auckland
-
places/1/4

http://www.snowyrangevision.com/laserSurgery.html

http://www.faqs.org/photo
-
dict/phrase/710/x
-
ray.html