Lec 3-4

Question 1

Chemiluminescence vs Fluorescence vs Phosphorescence

Answer 1

Chemiluminescence: e- excitation from chem rxn
Fluorescence: e- excitation from photon absorption
Phosphorescence: e- excitation from photon absorption, with triplet intermediate step

Question 2

Bioluminescence vs Thermal Radiation

Answer 2

Bioluminescence: e- excitation from chem rxn of luciferin
Thermal Radiation: Light emitted

Question 3

Evolutionary Pressure to create bioluminescence

Answer 3

Predation, evading predators, communication

Question 4

Continuum Wave (CW) Lasers

Answer 4

Continuous wave, lower power

Question 5

Pulsed Lasers

Answer 5

Short pulses, higher power

Question 6

Properties of lasers

Answer 6

Coherent, monochromatic, polarized and directional

Question 7

Applications of lasers

Answer 7

Cutting, communication, printing, scanning

Question 8

Types of waves

Answer 8

• Spherical Waves
• Planar Waves

Question 9

Huygen-Fresnel’s Principle

Answer 9

All points on a wavefront are the source of a new wave.

Question 10

Superposition Principle

Answer 10

Because waves can interfere constructively or destructively,
the result of superpositioned waves is their sum.

Question 11

Refraction

Answer 11

When crossing into another medium, light takes the path of shortest time, not the path of shortest distance
- (light is slower if index of refraction is high)

Question 12

Diffraction

Answer 12

Interference or bending of waves around obstacle

Question 13

Optical components for light manipulation

Answer 13

• Pinholes and Irises
• Mirrors
• Beam Splitters
• Filters
• Lenses
• Prisms
• Gratings
• Polarizers
• Optic Fibers`

Question 14

Pinholes

Answer 14

• Control amount of light entering a system
• Allows for formation of an image on a screen

Question 15

Pinhole examples

Answer 15

• Human iris
• Pinhole eyes of some animals
• Pinhole camera

Question 16

Mirrors

Answer 16

• Reflect light
• Flat or Curved
• Metallic or Dielectric

Question 17

Dielectric mirror

Answer 17

Are made from systems of thin lenses.

Layers of oil, water and air allow light to interfere constructively/destructively.

Question 18

Snell’s Law

Answer 18

n1sinθ_1=n2 sinθ_2

Question 19

Total internal reflection

Answer 19

• When
  
  • n1 > n2
  • θ_1 > 90
• As light θ_1 increases, more light is reflected than refracted

Question 20

Critical angle (θ_c)

Answer 20

θ_1 when θ_2 is 90°
(angle of incidence when angle of refraction is 90°)

Question 21

Filters

Answer 21

Selective for specific wavelengths

Question 22

Edge filters

Answer 22

Long Pass/Short Pass

Question 23

Long Pass Filters

Answer 23

Allow passage of long wavelengths, block short wavelengths

Question 24

Short Pass Filters

Answer 24

Allow passage of short wavelengths, block long wavelengths

Question 25

Lens equations

Answer 25

1/f=1/d_i +1/d_o M = -d_i/d_o = hi/ho

Question 26

Multiple Lens Equations

Answer 26

1/f = 1/f_1 + 1/f_2 M = -f_2/f_1

Question 27

Rayleigh Length

Answer 27

Describes beam waist at focal point

Question 28

Prisms

Answer 28

Larger refractive index for smaller wavelengths --> Different wavelengths refracted at different angles --> White light separated

Question 29

Gratings

Answer 29

Harnesses wave diffraction and interference to separate white light

Question 30

Polarizers

Answer 30

- Select light based orientation of electrical field - Total polarization of reflected ray achieved Brewters's angle

Question 31

Brewster's angle (θ_B)

Answer 31

θ_1 when θ_2 = 90° - θ_1 (incident angle when refracted angle equal to 90 - incident angle) or (angle between refracted ray and reflected ray)

Question 32

Brewster angle formula (derived from Snell's Law)

Answer 32

θ_B = arctan(n2/n1), n1 small and n2 large

Question 33

Critical angle formula (derived from Snell's Law)

Answer 33

θ_c = arcsin(n2/n1), n1 large and n2 small

Question 34

Optical fibers

Answer 34

- Harnesses total internal reflection to transport light - Incident angle larger or equal to critical angle

Question 35

Optical fiber types

Answer 35

- Step index (aka multimode): Multiple incident angles allowed - Graded index: refractive index dependent on distance from central axis - Single mode: Single incident angle allowed to preserve signal purity

Question 36

Examples of Light manipulation in biology

Answer 36

ex: Gratings in butterflies ex: Algae as lenses ex: Optical fibers in sea sponge ex: Animals with pinhole vision ex: Animals with bifocal lenses

Question 37

Describe how can optical components be used to measure ballistic photons through tissue.

Answer 37

Mirrors, lenses, beam splitters, optical fibers and filters are used together to use measure ballistic photons. ex: Optical Coherence Tomography (OCT) Strength: High resolution Weakness: Can't penetrate through deep tissues

Question 38

Define Structural Coloration

Answer 38

Colour visible on an object due to its structure, not luminescence. ex: Butterfly wings using gratings

Question 39

Incident Angle of Acceptance in optical fibers

Answer 39

sinθ = √ (n1^2 - n2^2 )