PPT of igce physics

1. 3.3 Electromagnetic Spectrum
Physics IGCSE
Madiha Shakil

2. Objectives
 Describe the main features of the electromagnetic spectrum in order of wavelength
 State that all electromagnetic waves travel with the same high speed in a vacuum
 Describe typical properties and uses of radiations in all the different regions of the
electromagnetic spectrum including:
 radio and television communications (radio waves)
 satellite television and telephones (microwaves)
 electrical appliances, remote controllers for
 televisions and intruder alarms (infrared)
 medicine and security (X-rays)
 Demonstrate an awareness of safety issues regarding the use of microwaves and X-
rays
 State that the speed of electromagnetic waves in a vacuum is 3.0 × 108m/s and is
approximately the same in air

3. Electromagnetic Wave
 An electromagnetic wave is a wave that consists of oscillating
electric and magnetic fields, which radiate outward from the
source at the speed of light.

5. EM Waves
 Can travel through vacuum.
 Travel in space at a speed of 300 000 km/s – usually called
speed of light. The speed of light in air is only 0.03% slower,
and c in either medium is usually just rounded off to 3.00 x 108
m/s.
 Transverse waves. Because both electric and magnetic fields
oscillating perpendicular to each other as it progresses.
 Transfer energy and not the medium
 Wave equation (v=fλ) is applicable for all EM Waves.
 Its speed and wavelength changes when it enters from one
medium to another (Frequency doesn’t) (Refraction)
 They obey the law of reflection and refraction.
 They carry no electric charge.

6. EM Waves - Energy
Different electromagnetic waves carry different amounts of
energy.
For example, microwaves carry less energy than X-rays.
 The amount of energy carried by an electromagnetic wave
depends on the wavelength:
the shorter the wavelength, the higher its energy.
 Wavelength and frequency are linked properties of a wave:
the shorter the wavelength, the higher its frequency.
 So, frequency also tells you about the energy of a wave:
the higher its frequency, the higher the energy.

7. Radio Waves
 Lowest frequencies and highest wavelength.
 Radio waves of longer wavelength can travel around obstacles.
 Types: Long, medium waves, VHF, UHF and microwaves.
 Uses:
 Long waves: long distance AM radio
 Medium waves: local AM radio
 Short Waves: AM Radio
 VHF: FM radio
 UHF: TV broadcasts

8. Microwaves
Microwave: mobile phones, tv and
communications satellite because
they can penetrate the atmosphere,
WI-FI, Telephone links, Radar,
Heating effect is used in microwave
ovens.
Microwaves enters food and cause
the water molecule to vibrate
vigorously. The vibration of
molecules generates heat that
spreads throughout the food

9. Infrared Radiation
 As object heats up, it produces infrared. The shorter
wavelengths invisible to the eye is called infrared light and
as the object is heated more (it becomes “red hot”) the
radiation enters the visible light spectrum of EM.
 You can see IR light using a camera lens.
 Uses of IR: Security alarms and lamps automatically
switched on if a person causes a disturbane in an IR
pattern.

10. Light
 Light is used in optical fibres in medical uses and
sending telephone signals. In endoscopes light is send
through bundle of optical fibers to look inside the body.
Also in optical fibres pulse of laser light is used carry
telephone calls.

11. Ultraviolet Radiation
 Very hot objects emit radiation beyong visible violet, this is
called ultraviolet radiation.
 It is harmful to the living cell and can cause cancer
(specially for paler skin) or damage the retine of the eye.
 Uses: Sterilizing equipment to kill bacteria.
 Fluorescence, some materials fluoresce when they
absorb UV, they convert its energy to visible light and glow.

12. X-Rays
 Short-wavelength X-rays are extremely penetrating. Lead
can reduce their strength. They are used to kill cancer cells
in radiation therapy
 Long-wavelength X-rays can pass through flesh and not
bones and used in medicine to see fractures. In airport
security systems and to see flaws inside metals and pipe
joints etc.

13. Gamma Rays
 Comes from radioactive materials.
 Like X-rays can be used in the
treatment of cancer and for taking
X-ray type photographs.
 Also used for sterilizing food and
medical equipment.
 There is a procedure called
gamma knife procedure, which
directs gamma rays to brain
tumours to kill cancer cells.

14. Ionizing Radiation
 UV, X-ray and gamma rays cause ionization – they strip
electrons from atome in the path. The atoms are left with an
electric charge, and then known as ions.
Ionization is harmful because it can kill or damage living cells
or make them grow abnormally (mutation) as cancers.
 Microwaves are not ionizing but they are absorbed by your
body and may cause heating of body tissues. This heating
could result in medical conditions, possibly including cancer, but
there is no conclusive evidence.