Chapter 7: Light

capricioustelephoneUrban and Civil

Nov 16, 2013 (3 years and 6 months ago)

58 views

Chapter 7: Light

Electromagnetic Wave

Fig 7.2



Electromagnetic Radiation



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 Radiation


“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



Dispersion (Spreading)



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