MatE 21 Optical Properties (Concepts) Flashcards
response of a material to electromagnetic radiation
Optical Property
refers to packets of discrete energy
PHOTON
When light strikes a solid, it may absorb the photon causing the transition of an electron to a __________.
higher energy state.
The electric field of EM radiation can interact with the electron cloud which would induce _________.
electronic polarization (change in shape of the electron cloud).
Change in direction is described by _____’s law
Snell’s law
If there is no angle θ2 fulfilling Snell’s law, then radiation would undergo ________
total internal reflection
The (1)_________ or ion, the (2)_________ will be the electronic (3)___________, the (4)________ the velocity
(1) larger an atom
(2) greater
(3) polarization
(4) slower
very __________ energy is needed to cause e- excitation
small
Conductors are usually ________ since electrons in the solid can easily absorb light.
opaque
Most of the absorbed radiation is then reemitted from the surface in the form of visible light of the same wavelength
Reflection
In insulators, very _________ energy is needed to cause e- excitation/transition
large
If energy of light _ band gap of material
Light won’t be absorbed since electron has no electron state it can occupy.
<
If energy of light _ band gap of material
Light would be absorbed since the electron can cross the band gap and occupy a higher energy state.
>
For a translucent material, color seen is the ______ color of the wavelength absorbed.
COMPLEMENTARY
Impurities in diamonds impart defect levels causing ________
different colors
Impurities introduce (1) ________ energy levels in the band gap which causes (2) __________processes to happen.
(1) impurity/trap
(2) multi-step decay (recombination)
For inherently transparent crystalline materials, defects causes ____________.
total internal reflection
For polymers, _________ is important in determining its optical properties.
crystallinity
Because the refractive index of the crystalline region is (1) ________ than that of the amorphous region, increasing the (2) ________ of the polymer would lead to (3) ________ turning the polymer from transparent to translucent/opaque.
(1) higher
(2) %crystallinity
(3) higher scattering
the optical behavior of a solid is dependent on how it interacts with _________.
EM radiation
➢Possible interactions between matter and light include _______, _________, _________, and __________.
refraction, reflection, absorption, transmission
➢Electromagnetic radiation may be __________ by causing the excitation of electrons to a higher energy state.
absorbed
