Glass analysis

Glass is ___________ at short range, but ________________ at large range

ordered, amphorous

Speed of light in vacuum (no interaction with matter)

c ≈ 3 x 10^8 m/s

Speed in matter

𝐯 < 𝐜

refractive index 𝐧 = 𝐜/𝐯

n= refractive index
c= speed of light in a vacuum
v= speed of light in material

Light is slowed down because of

interaction with the electrons of the material

What happens when the electric field of light interacts with electrons in a material?

It drives the electrons at the same frequency

What is the result of the superposition of the electric fields in a material?

A field of slower speed but the same frequency

The refractive index is linked to

the polarizability of the medium.

The chemical composition defines the density which then defines the refractive index of the glass

true

as temperature increases, refractive index and density

decreases

as density increases

refractive index increases

What is dispersion?

Dispersion is the separation of light into its constituent colors due to the wavelength-dependent refractive index of a material.

How does dispersion influence optical phenomena?

Dispersion leads to the separation of a medium's light into its constituent colors

Abbe number

Measures possible chromatic abberation in a lens material, the higher the index the lower the abbe number the more abberation

steeper slope = smaller dispersion and higher abbe number 𝛎 𝐃

false; Steeper slope= larger dispersion and lower abbe number

Which sequence is correct?

nf>nd>nc

immersion method

method used to measure RI of glass by immersing glass in different oils with known RIs and observing which oil the glass disappears in

Contrast (Acutance, Sharpness) occurs when

Enough difference in RI for you to see a interface

Glass not seen

When using high RI immersion oil that closely matches glass, minimizing refraction and maximizing clarity of the sample.

Becke line

A bright halo that is observed near the border of a particle immersed in a liquid of a different refractive index

nobj > noil

halo appears on outside of object

nobj < noil

Halo appears on outside of oil

Determining if the glass is in a medium of higher or lower RI step 1:

place sample at focus

Determining if the glass is in a medium of higher or lower RI step 2:

Lower the stage (increase the distance between sample and objective)

Determining if the glass is in a medium of higher or lower RI step 3:

The bright line (Becke line) moves towards the medium of higher RI

The dispersion is usually _________ for glass than for oil

lower

GRIM

glass sample is placed in a medium (often a liquid) with a known refractive index. By adjusting the temperature and comparing the refractive indices, the index of the glass can be accurately measured.

Annealing

Heating the glass to homogenize it

Removing stress

removing density inhomogeneity = reducing dispersion of RI value