Transcript Aim: How can we explain the Electromagnetic Spectrum?

Aim: How can we explain
the Electromagnetic
Spectrum?
Do Now:
A light wave in a vacuum is traveling with a frequency of
6.2 x 1010 Hz. What is the wavelength?
v = fλ
3.0 x 108 m/s = (6.2 x 1010 Hz)λ
λ = 4.8 x 10-3 m
The Electromagnetic
Spectrum
• The speed of all waves of
the EM spectrum in a
vacuum is the speed of
light (c).
8
= 3.00 x 10 m/s
• What type of wave has the
longest wavelength?
Long Radio Waves
• What type of wave has the
shortest wavelength?
Gamma Rays
•About what is the
wavelength of
visible light?
-7
10
m
• What type of wave has
the highest frequency?
Gamma Rays
• What type of wave has
the lowest frequency?
Long Radio Waves
Visible light only makes up about 2% of the EM spectrum!
• What color light has a
frequency between 6.10 x 1014
Hz and 5.20 x 1014 Hz?
GREEN
• What color light has a
frequency between 5.03 x 1014
Hz and 4.82 x 1014 Hz?
ORANGE
In a vacuum, a
monochromatic beam of light
has a frequency of 6.3 x 1014
Hz. What color is the light?
BLUE
Finding Frequency or Wavelength
of an Electromagnetic Wave
• Use the equation
v = fλ
• Just remember that any EM wave has a
velocity of….
3.00 x
8
10
m/s
Hence, c = fλ
Determine the color of a
ray of light with a
-7
wavelength of 6.21 x 10 m.
c = fλ
(3.00 x 108 m/s) = f(6.21 x 10-7 m)
f = 4.83 x 1014 Hz
(ORANGE)
• When asked to refer to a
specific color’s
frequency, choose the
value to the LEFT of that
color!
What is the wavelength of red
light?
c = fλ
3 x 108 m/s = (4.82 x 1014 Hz) λ
λ = 6.2 x
-7
10
m
Calculate the wavelength of
WPLJ (95.5 fm)
c = fλ
Hint: fm radio transmits in
megahertz
(3.00 x 108 m/s) = (95.5 x 106 Hz) λ
λ = 3.14 m
In a vacuum, all
electromagnetic waves
have the same
(1)Wavelength
(2)Frequency
(3)Speed
(4)amplitude
A 2.00 x 106 Hz radio signal is sent a
distance of 7.30 x 1010 meters from
Earth to a spaceship orbiting Mars.
Approximately how much time does
it take the radio signal to travel from
Earth to the spaceship?
(1) 4.11 x 10-3 s
(2) 2.43 x 102 s
(3) 2.19 x 108 s
(4) 1.46 x 1017 s
How long does it take light to travel
from the Sun to the Earth?