Physics 1, II-Rosal, PSHS-MC, Group 6

1. 
Electromagnetic Spectrum
Physics 1, Group 6, Rosal 2015

2. James Clerk
Maxwell
 With the equations he
formulated on
electromagnetic
induction, he found
that these equations
had a speed of ~3.00 x
108 m/s w/c is equal to
the speed of light
 Discovered the nature
of light (as
electromagnetic waves)
 Light wave as a
transverse wave

3. Electromagnetic
Radiation
 Made of electric and magnetic
fields vibrating, acc to wave
theory, at right angles to one
another and moving through space at
the speed of light
 Form of ENERGY that can travel
through empty space
 Classified across the spectrum by
its wavelength
 A transverse wave consisting of
oscillating electric and magnetic

5. Electromagnetic Spectrum
 All EM waves travel at the same speed in
a vacuum, they differ from one another
in their frequency & wavelength
 Classification of EM waves according to
frequency
 Light is simple EM waves in this range
of frequencies
 Ex. Accelerating electric charge ->
radiate in electric and magnetic fields

7. Radio waves
 Examples: radio stations, stars, aircraft and
shipping bands, TV and fm radio,
astronomical bodies, lightning, can
transmit info
 Low wavelength, low frequency, low
energy

8. Microwaves
 Microwaves in space are used by astronomers to
learn about the structure of nearby galaxies, and
our own Milky Way!
 Can penetrate through smoke, haze, clouds, and
even light rain
 Ex. Microwaves radar, transmit data, satellite
imagery

9. Infrared
 Our skin emits infrared light, which is why we can
be seen in the dark by someone using night vision
goggles. In space, IR light maps the dust between
stars.
 Even that we can not see or hear infrared, we can
feel it at our skin temperature sensors.

10. Color Frequency Wavelength
violet 668–789 THz 380–450 nm
blue 606–668 THz 450–495 nm
green 526–606 THz 495–570 nm
yellow 508–526 THz 570–590 nm
orange 484–508 THz 590–620 nm
red 400–484 THz 620–750 nm
Visible spectrum 

11. Visible Spectrum
 Portion of the electromagnetic
spectrum that is visible to (can be
detected by) the human eye.
 corresponds to a band in the
vicinity of 400–790 THz.
 Reflects light off objects from any
light source
 Visible sunlight passes through the
earth’s atmosphere and reflects off
objects allowing us to see them

13. Why does a CD reflect rainbow colors?
 Like water drops in falling rain, the CD separates white
light into all the colors that make it up. The colors you
see reflecting from a CD are interference colors, like the
shifting colors you see on a soap bubble or an oil slick.
 You can think of light as as being made up of waves-like
the waves in the ocean. When light waves reflect off the
ridges on your CD, they overlap and interfere with each
other. Sometimes the waves add together, making
certain colors brighter, and sometimes they cancel each
other, taking certain colors away.

14. Why does a CD reflect rainbow colors?
 On a CD, the surface is mirrored so the rainbow
colors are much more intense.
 the angle controls the path difference.

15. Ultraviolet
 Ex. Sun, stars and other “hot objects in
space emit UV radiation, “ultraviolet”
because its frequency is just a bit
higher than visible violet light, in
gadgets, black light lamps
 10 nm- 400 nm

16. X-Ray
 Naturally emitted by space objects like neutron stars, black
holes, binary stars, remnants of super nova, stars, comets,
and even our own sun
 X-ray images are produced when they are absorbed by what
they strike and, leaving shadows on the film that imprints in
an image
 3nm – 0.3 nm

17. Gamma Rays
 Smallest wavelength
 Ex. Nuclear power plants, big particle accelerators,
stars, radiotherapy- used to kill cancer cells (gamma
knife), kills microorganisms in food through
irradiation, sterilizing medical equipment
 Biggest gamma ray generator: naturally produced
in the hottest regions of the universe

19. Light Comparison (f and λ)
LIGHT COMPARISON
Name Wavelength Frequency (Hz)
Gamma Ray Less than 0.02 nm More than 15 EHz
X-Ray 0.01 nm – 10 nm 30 EHz – 30 PHz
Ultraviolet 10 nm – 400 nm 30 PHz – 760 THz
Visible 390 nm – 750 nm 770 THz – 400 THz
Infrared 750 nm – 1mm 400 THz – 300 GHz
Microwave 1 mm – 1 m 300 GHz – 300 MHz
Radiowaves 1 mm – 100, 000 300 GHz – 3 Hz
km