# Chapter 7: Light

Urban and Civil

Nov 16, 2013 (4 years and 7 months ago)

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Chapter 7: Light

Electromagnetic Wave

Fig 7.2

Both “fields” vary together

Transverse Waves.

Electromagnetic (EM)
Spectrum

Fig 7.3

Range of Frequencies

(or Wavelengths)

Visible Light only a

small portion.

Sources of Light

Matter constantly emits and absorbs radiation

Emission mechanism:

Accelerated, oscillating “charges” produce EM Waves

Different accelerations lead to different frequencies

Key Terms: Luminous and Incandescent.

“Blackbody”

Idealized material

Perfect emitter ; perfect absorber

Increasing Temperature

results in?...

Spectrum of Sun light.

Fig 7.4

Fig 7.5

Properties of Light:

Two “Models”

“Light Ray” Model

Particle
-
like view

Photons travel in
straight lines

Best explains

Mirrors

Prisms

Lenses

“Wave” Model

Traces motions of
wave fronts

Best explains

Interference

Diffraction

Polarization

http://hyperphysics.phy
-
astr.gsu.edu/hbase/ligcon.html#c1

Light interacts with matter

Fig 7.6

Interaction begins at the
surface and depends upon?

Possible Interactions?

Transparent vs Opaque?

Reflection

r
i

Fig 7.11

Diffuse Reflection

Fig 7.7

Fig 7.10

Why is the sky blue at noon?

(A Closer Look)

Another Behavior of Light

Refraction

Light crossing a boundary
surface and changing
direction (bending)

Reason?

Differing densities.

Fig 7.15

r
i

Magnitude (Amount)

of Refraction

Depends upon?:

1.
Angle which light strikes
the surface

2.
Ratio of the speeds of
light in the two materials

#2 helps define the
Index of Refraction

of a substance

Table 7.1

Example 7.1

Mirages

Similar to Fig 7.17

“Mirage” is due to Refraction!

Wet Highway?

Dispersion and Colors

White light

Wavelength and frequency

are related

Dispersion and Colors

Rainbows

(A Closer Look)

Fig 1.15

Box Fig 7.7

Optics

The use of lenses to form images

Concave lenses

Diverging

Convex lenses

Converging

BOX FIG 7.1

The Human Eye

Nearsightedness (myopia)

corrected with a:

Farsightedness (hyperopia)

corrected with a:

Concave Lens

Convex Lens.

BOX FIG 7.4

Uses a convex lens to

change focal length

The nature of light

Wave
-
like behavior

Diffraction & Interference

Fig 7.19

Wave
-
like behavior
-

Polarization

Alignment of
electromagnetic fields

Unpolarized vs.
Polarized light

(Figs 7.20 and 7.21)

The nature of light:

Particle
-
like behavior

“Quanta” and Photons

Example 7.3

Photoelectric Effect

Fig 7.23

Next: Chapter 8

Atoms

and the

Periodic Properties