preview objectives electromagnetic waves chapter 13 section 1 characteristics of light

Preview

• Objectives

• Electromagnetic Waves

Chapter 13Section 1 Characteristics of Light

Section 1 Characteristics of LightChapter 13

Objectives

• Identify the components of the electromagnetic spectrum.

• Calculate the frequency or wavelength of electromagnetic radiation.

• Recognize that light has a finite speed.

• Describe how the brightness of a light source is affected by distance.


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.

Chapter 13

The Electromagnetic Spectrum

Section 1 Characteristics of Light


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 Equationc = f

speed of light = frequency wavelength

Click below to watch the Visual Concept.

Visual Concept

Chapter 13Section 1 Characteristics of Light

Electromagnetic Waves



• Waves can be approximated as rays. This approach to analyzing waves is called Huygens’ principle.

• Lines drawn tangent to the crest (or trough) of a wave are called wave fronts.

• In the ray approximation, lines, called rays, are drawn perpendicular to the wave front.



• Illuminance decreases as the square of the distance from the source.

• The rate at which light is emitted from a source is called the luminous flux and is measured in lumens (lm).

Chapter 13 Assignments

• Page 449 Practice A 1,2(2), 3(2)

Preview

• Objectives

• Reflection of Light

• Flat Mirrors

Chapter 13 Section 2 Flat Mirrors

Section 2 Flat MirrorsChapter 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.


Reflection of Light

• Reflection is the change in direction of an electromagnetic wave at a surface that causes it tomove 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.– Regular reflection is reflection from a smooth, shiny

surface such as a mirror or a water surface.


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.


Visual Concept


Angle of Incidence and Angle of Reflection


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.

Chapter 13

Image Formation by a Flat Mirror

Section 2 Flat Mirrors


Visual Concept


Comparing Real and Virtual Images


• Page 449 Practice A 1,2(2), 3(2)• P454 Section Review #2

How tall would a mirror have to be for a 6ft tall person to see their entire body?

6ft tall person, mirror?

mirrorperson

Preview

• Objectives

• Concave Spherical Mirrors

• Sample Problem

• Parabolic Mirrors

Chapter 13 Section 3 Curved Mirrors

Section 3 Curved MirrorsChapter 13

Objectives

• Calculate distances and focal lengths using the mirror equation for concave and convex spherical mirrors.

• Draw ray diagrams to find the image distance and magnification for concave and convex spherical mirrors.

• Distinguish between real and virtual images.

• Describe how parabolic mirrors differ fromspherical mirrors.


Concave Spherical Mirrors

• A concave spherical mirror is a mirror whose reflecting surface is a segment of the inside of a sphere.

• Concave mirrors can be used to form real images.

• A real image is an image formed when rays of light actually pass through a point on the image. Real images can be projected onto a screen.

Images

• Real – light rays actually pass through the point where the image is formed.

• Virtual – light rays appear to pass through the point where the image is formed but actually do not.

• Upright – Inverted• Reversed• Enlarged-Reduced

Mirrors

Flat or Plain

Concave

Convex

Curved Mirrors

• Focal point – the point where parallel incident rays converge when they are reflected.– For a concave mirror, the focal point is on the same

side as the source of light rays.– For a convex mirror the focal point is behind the

mirror from the source of the light rays.• Center of curvature- the center of the circle from which

the mirror is made.• Focal length is ½ the radius of curvature.

– Focal point is ½ way between center of curvature and the mirror.

Concave Mirror Image

Chapter 13

Image Formation by a Concave Spherical Mirror

Section 3 Curved Mirrors


Concave Spherical Mirrors, continued

• The Mirror Equation relates object distance (p), image distance (q), and focal length (f) of a spherical mirror.

1

p

1

q

1

f

1

object distance

1

image distance

1

focal length



• The Equation for Magnification relates image height or distance to object height or distance, respectively.

'–

image height image distancemagnification = –

object height object distance

h qM

h p


Visual Concept


Rules for Drawing Reference Rays for Mirrors

3 Rays (any 2)

• A ray passing through the focal point will be reflected parallel to the axis of the mirror.

• A ray parallel to the axis will be reflected through the focal point.

• A ray passing through the center of curvature of a mirror will be reflected back on itself.

Convex Mirror Image



• Ray diagrams can be used for checking values calculated from the mirror and magnification equations for concave spherical mirrors.

• Concave mirrors can produce both real and virtual images.


Visual Concept


Ray Tracing for a Concave Spherical Mirror

Replay


Sample Problem

Imaging with Concave Mirrors

A concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.


• Page 449 Practice A 1,2(2), 3(2)• P454 Section Review #2• Page 462 Practice B 1(5), 2(5) (4for answer+1 for rays)


Sample Problem, continued


1. Determine the sign and magnitude of the focal length and object distance.

f = +10.0 cm p = +30.0 cm

The mirror is concave, so f is positive. The object is in front of the mirror, so p is positive.




2. Draw a ray diagram using the rules for drawing reference rays.




3. Use the mirror equation to relate the object and image distances to the focal length.

–q

Mp

1

p

1

q

1

f

4. Use the magnification equation in terms of object and image distances.



5. Rearrange the equation to isolate the image distance, and calculate. Subtract the reciprocal of the object distance from the reciprocal of the focal length to obtain an expression for the unknown image distance.

1 1 1

–q f p



Substitute the values for f and p into the mirror equation and the magnification equation to find the image distance and magnification.

1 1 1 0.100 0.033 0.067– –

10.0 cm 30.0 cm cm cm cm

15 cm

15 cm– – –0.50

30.0 cm

q

q

qM

p



6. Evaluate your answer in terms of the image location and size.

The image appears between the focal point (10.0 cm) and the center of curvature (20.0 cm), as confirmed by the ray diagram. The image is smaller than the object and inverted (–1 < M < 0), as is also confirmed by the ray diagram. The image is therefore real.


Convex Spherical Mirrors

• A convex spherical mirror is a mirror whose reflecting surface is outward-curved segment of a sphere.

• Light rays diverge upon reflection from a convex mirror, forming a virtual image that is always smaller than the object.

Chapter 13

Image Formation by a Convex Spherical Mirror



Sample Problem

Convex Mirrors

An upright pencil is placed in front of a convex spherical mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.



Convex Mirrors

Given:

Because the mirror is convex, the focal length is negative. The image is behind the mirror, so q is also negative.

f = –8.00 cm q = –4.44 cm h’ = 2.50 cm

Unknown:

p = ? h = ?


• Page 449 Practice A 1,2(2), 3(2)• P454 Section Review #2• Page 462 Practice B 1(5), 2(5) (4for answer+1 for rays)

• Page 466 Practice C 3(5), 5(3), 6(4)• 7 Chapter Review 20(2), 34(6),36(3)

3 Rays (any 2)

• A ray passing through the focal point will be reflected parallel to the axis of the mirror.

• A ray parallel to the axis will be reflected through the focal point.

• A ray passing through the center of curvature of a mirror will be reflected back on itself.



Convex Mirrors

Diagram:



Convex Mirrors

2. Plan

Choose an equation or situation: Use the mirror equation and the magnification formula.

1 1 1

– and – 'p

h hp f q q

1 1 1 '

and –h q

Mp q f h p

Rearrange the equation to isolate the unknown:



Convex Mirrors

3. Calculate

Substitute the values into the equation and solve:

1 1 1–

–8.00 cm –4.44 cm

1 –0.125 –0.225 0.100–

cm cm cm

10.0 cm

p

p

p



Convex Mirrors3. Calculate, continued

Substitute the values for p and q to find the magnifi-cation of the image.

10.0 cm– ' – (2.50 cm)

–4.44 cm

5.63 cm

ph h

q

h

Substitute the values for p, q, and h’ to find the height of the object.

–4.44 cm

– – 0.44410.0 cm

qM M

p


Visual Concept


Ray Tracing for a Convex Spherical Mirror


Parabolic Mirrors

• Images created by spherical mirrors suffer from spherical aberration.

• Spherical aberration occurs when parallel rays far from the principal axis converge away from the mirrors focal point.

• Parabolic mirrors eliminate spherical aberration. All parallel rays converge at the focal point of aparabolic mirror.

Chapter 13

Spherical Aberration and Parabolic Mirrors



Visual Concept


Reflecting Telescope

Preview

• Objectives

• Color

• Polarization of Light Waves

Chapter 13 Section 4 Color and Polarization

Section 4 Color and PolarizationChapter 13

Objectives

• Recognize how additive colors affect the color of light.

• Recognize how pigments affect the color of reflected light.

• Explain how linearly polarized light is formed and detected.


Color

• Additive primary colors produce white light when combined.

• Light of different colors can be produced by adding light consisting of the primary additive colors (red, green, and blue).


Visual Concept


Additive Color Mixing


Color, continued

• Subtractive primary colors filter out all light when combined.

• Pigments can be produced by combining subtractive colors (magenta, yellow, and cyan).


Visual Concept


Subtractive Color Mixing


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.

Chapter 13

Linearly Polarized Light

Section 4 Color and Polarization

Chapter 13

Aligned and Crossed Polarizing Filters

Section 4 Color and Polarization

Crossed FiltersAligned Filters


Polarization of Light Waves

• Light can be polarized by reflection and scattering.

• At a particular angle, reflected light is polarized horizontally.

• The sunlight scattered by air molecules is polarized for an observer on Earth’s surface.


Visual Concept


Polarization by Reflection and Scattering

preview objectives electromagnetic waves chapter 13 section 1 characteristics of light

Documents

reflection of light

characteristics of light

light source

angle of reflection

diffuse reflection of

visible light

f speed of light

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