Lec 5-6

Question 1

What is the main light scatterers in biological systems?

Answer 1

Lipids

Question 2

What are the interactions of light with matter? (6)

Answer 2

Reflection, refraction, absorption, emission, scattering, interference/resonance

Question 3

Absorption of light in biological organisms is due to which molecule(s) (2)

Answer 3

Pyrroles, which form porphyrins

Question 4

Specific examples of porphyrins that absorb light (3)

Question 5

Specific examples of light-absorbing biomolecules

Answer 5

Carotenoides, ferredoxins, flavins, melanin

Question 6

The type scattering (Mie or Rayleigh) depend on…

Answer 6

the size of the object

Question 7

Mie Scattering occurs in which cellular components?

Answer 7

Mitochondria, organelles, collagen fibril striations and macromolecular aggregates.

Question 8

Rayleigh scattering occurs in which cellular components?

Answer 8

Collagen fibril striations, macromolecular aggregates, and membranes.

Question 9

What is the thickness of cellular membrane?

Answer 9

5 nm

Question 10

What is the biological optical window?

Answer 10

650 - 950 nm, the range that avoids absorption

Question 11

What is a ballistic photon?

Answer 11

Photons that do not scatter nor get absorbed after they pass through tissues. They have a high velocity.

Question 12

When photon passes through tissue, which type are the most common?

Answer 12

Diffusive photons (photons that are scattered)

Question 13

What is an application of red lasers in biomedical devices?

Answer 13

Pulseoximeter

Question 14

What is the name of compounds that absorb light (in tissue)?

Answer 14

Pigments

Question 15

What is the formula for absorption or scattering coefficient? (they have the same form)

Answer 15

μ[a] = p[a]σ[a]
μ[s] = p[s]σ[s]

Question 16

What is the formula for effective cross-sectional area?

Answer 16

σ[a] = Q[a] A
σ[s] = Q[s] A

Question 17

What is the formula for transmitted light?

Answer 17

T = e ^ (-μ[a] L)
T = e ^ (-μ[s] L)

Question 18

Formula for total intensity of light at a distance z

Answer 18

I(z) = I[0] e ^ (-μ z)
where μ = μ[a] + μ[s]

Question 19

Define earth’s energy budget

Answer 19

the balance between radiant energy (input) and the dissipation/consumption of energy (output)

Question 20

What are the factors for earth’s surface temperature? (2)

Answer 20

solar radiation, earth’s hot core