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Light and Reflection
Chapter 13
Table of Contents
• Characteristics of Light
• Flat Mirrors
• Color and Polarization

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Section 1 Characteristics of
Light
Chapter 13
Electromagnetic Waves
• 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.
• Light is a form of electromagnetic radiation.
• The electromagnetic spectrum includes more than
visible light.

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The Electromagnetic Spectrum
High Frequency
Short Wavelength
High Energy
Low Frequency
Long Wavelength
Low Energy

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Chapter 13
The Electromagnetic Spectrum
Section 1 Characteristics of
Light

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Section 1 Characteristics of
Light
Chapter 13
Electromagnetic Waves, continued
• Electromagnetic waves vary depending on frequency
and wavelength.
• All electromagnetic waves move at the speed of light.
The speed of light, c, equals
c = 3.00  108 m/s
• Wave Speed Equation
c = fl
speed of light = frequency  wavelength

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Chapter 13
Electromagnetic Waves
Section 1 Characteristics of
Light

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EMS Practice Concepts
• Use your reference table to determine:
– Which color of light has the shortest l?
– What is the color of light that possesses a
frequency of 5.10 x 1014 hz?
– A photon of light has a frequency of
4.0 x 1010 hz. What range of the EMS is it in?
– Which photon has more energy
• Gamma or infared?
Violet
Yellow
Microwaves
Gamma

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Multiple Choice, continued
2. Which of the following statements is true about the
speeds of gamma rays and radio waves in a
vacuum?
F. Gamma rays travel faster than radio waves.
G. Radio rays travel faster than gamma rays.
H. Gamma rays and radio waves travel at the same
speed in a vacuum.
J. The speed of gamma rays and radio waves in a
vacuum depends on their frequencies.
Standardized Test Prep
Chapter 13

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Multiple Choice, continued
2. Which of the following statements is true about the
speeds of gamma rays and radio waves in a
vacuum?
F. Gamma rays travel faster than radio waves.
G. Radio rays travel faster than gamma rays.
H. Gamma rays and radio waves travel at the same
speed in a vacuum.
J. The speed of gamma rays and radio waves in a
vacuum depends on their frequencies.
Standardized Test Prep
Chapter 13

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EMS Short Response Practice Problem
– What is the frequency of a photon of light that has a
wavelength of 3.8 x 10-7 m?
• What region of the EMS is it located?

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Short Response, continued
13. X rays emitted from material around compact
massive stars, such as neutron stars or black holes,
serve to help locate and identify such objects. What
would be the wavelength of the X rays emitted from
material around such an object if the X rays have a
frequency of 5.0  1019 Hz?
Standardized Test Prep
Chapter 13

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Short Response, continued
13. X rays emitted from material around compact
massive stars, such as neutron stars or black holes,
serve to help locate and identify such objects. What
would be the wavelength of the X rays emitted from
material around such an object if the X rays have a
frequency of 5.0  1019 Hz?
Answer: 6.0  10–12 m = 6.0 pm
Standardized Test Prep
Chapter 13

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Section 2 Law of Reflection and
Flat Mirrors
Chapter 13
Objectives
• Distinguish between specular and diffuse reflection
of light.
• Apply the law of reflection for flat mirrors.
• Describe the nature of images formed by flat mirrors.

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Section 2 Flat Mirrors
Chapter 13
Reflection of Light
• Reflection is the change in direction of an
electromagnetic wave at a surface that causes it to
move away from the surface.
• The texture of a surface affects how it reflects light.
– Diffuse reflection is reflection from a rough, texture
surface such as paper or unpolished wood.
– Specular reflection is reflection from a smooth,
shiny surface such as a mirror or a water surface.

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Section 2 Flat Mirrors
Chapter 13
Reflection of Light, continued
• The angle of incidence is the the angle between a
ray that strikes a surface and the line perpendicular
to that surface at the point of contact.
• The angle of reflection is the angle formed by the
line perpendicular to a surface and the direction in
which a reflected ray moves.
• The angle of incidence and the angle of reflection are
always equal.

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Chapter 13
Angle of Incidence and Angle of Reflection
Section 2 Flat Mirrors

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Section 2 Flat Mirrors
Chapter 13
Flat Mirrors
• Flat mirrors form virtual images that are the same
distance from the mirror’s surface as the object is.
• The image formed by rays that appear to come from
the image point behind the mirror—but never really
do—is called a virtual image.
• A virtual image can never be displayed on a physical
surface.

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Chapter 13
Image Formation by a Flat Mirror
Section 2 Flat Mirrors

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Chapter 13
Comparing Real and Virtual Images
Section 2 Flat Mirrors

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Section 4 Color and Polarization
Chapter 13
Polarization of Light Waves
• Linear polarization is the alignment of electro-
magnetic waves in such a way that the vibrations of
the electric fields in each of the waves are parallel to
each other.
• Light can be linearly polarized through transmission.
• The line along which light is polarized is called the
transmission axis of that substance.

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Chapter 13
Linearly Polarized Light
Section 4 Color and Polarization

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Chapter 13
Aligned and Crossed Polarizing Filters
Section 4 Color and Polarization
Crossed Filters
Aligned Filters

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Chapter 13
Polarization by Reflection and Scattering
Section 4 Color and Polarization