OUTLINE
1. Intensity of electromagnetic wave
(continued)
2. Polarization (mostly about light)
3. Reflection and refraction of light
Sample Problem 33-1
An observer is 1.8 m from an isotropic point source of
light with power Ps = 250 W. Calculate the rms values
of the electric and magnetic fields due to the source at
the position of the observer.
QUIZ
The intensity of the solar radiation near the equator is
1370 W/m2 at noon. What is the radiation pressure, if
the radiation is completely absorbed?
• 4.6 x 10-6 Pa. It is feeble, but …
An artist’s view of the Cosmos 1 satellite with
the solar sail unfolded. But the launching
rocket failed.
(Picture from Wikipedia)
• Radiation pressure, together with gas pressure,
prevents stars from collapsing due to gravity.
CHECKPOINT 4
Four pairs of polarizing sheets are placed in the
path of initially unpolarized light, with the polarizing
direction of each sheet indicated by the dashed line.
Which pair lets the largest fraction of light through?
Which pair lets through the least?
QUIZ
45°
45°
(a)
(b)
Which arrangement of polarizing sheets lets more
light through?
Arrangement a.