Deck 1 Flashcards
Light Rays + Introduction to Microscope Optics
Light has both ____ and ______ properties
Electrical and Magnetic Properties
what is the speed of light?
300,000 km/s or 3x10 ^17nm/s
The electromagnetic spectrum contains —– light, ———– light, —– and —- light.
Monochromatic light contains a _____ wavelength.
White light includes ___ wavelengths in the spectrum.
Black Light includes ___ wavelengths reflected. everything is being absorbed.
Visible light, monochromatic light, dark and white light.
Monochromatic light contains a single wavelength.
White light includes all wavelengths.
Black light includes no wavelengths.
What is a wave front?
A wave front is a surface that connects the same points on adjacent waves.
what is a wave normal?
A wave normal a line drawn perpendicular to the wave front. It represents wave direction.
what is a light ray?
A light ray is the propagation of light energy. This is equivalent to the path followed by a photon.
Define Anisotropic.
Anisotropic is when an object or substance has a physical property with a different value depending on direction of measurement.
Define Isotropic.
Isotropic is when an object or substance has a physical property that produces the same value when measured in all directions.
Photons possess _____, not mass. Waves are described as ________ radiation.
energy/ electromagnetic radiation.
What is the wave theory?
The wave theory says that radiant energy (Light) has ELECTRICAL and MAGNETIC properties.
(aka electric and magnetic properties that vibrate in all directions.)
If light travels through a substance, the velocity _____.
Explain this using the formula V = f x (wavelength)
Decreases.
When monochromatic light passes through a substance, f remains the same, but wavelengths bunch up, decreasing V.
Does the structure of a material change the velocity of light as it passes through?
yes
What are some characteristics of an Isotropic material?
- Does not depend on direction
- has a single refraction index.
- contains minerals that crystallize in the isometric crystal system.
What are some characteristics of an Anisotropic material?
- Refraction index is dependent on direction.
- will have a range of RI between two extremes:
a) Uniaxial and b) Biaxial.
What are Uniaxial Minerals?
What are Biaxial Minerals?
- Uniaxial minerals are characterized by 2 refraction indices and 1 optic axis. (Minerals of Tetragonal & Hexagonal C.S.)
- Biaxial minerals are characterized by 3 refraction Indices and 2 optic axes. (Minerals of Orthorhombic, Monoclinic and Triclinic systems).
What is Birefringence?
Also known as Double Refraction, Birefringence is an optical property of certain materials that cause a single ray of light to be separated into two rays.
define double refraction.
Double refraction occurs when a ray of light travels through an anisotropic material and is split into two rays, both traveling in different directions due to the difference in RI values, with different velocities.
The Fast ray has a ____ velocity and ____ RI
The Slow ray has a ____ velocity and ____ RI
The fast ray has a high velocity and a LOW RI
The slow ray has a low velocity and a HIGH RI
What happens to light travelling along the C-axis of a uniaxial mineral?
When light travels along the c-axis, the light rays vibrate perpendicular. the light is not split into two rays.
Define Retardation.
The amount that the slow ray lags behind the fast ray as it exits the crystal.
This is related to the difference in RI values and the THICKNESS of the material.
retardation = d(n1-n2)
What is a principle section?
Any section through the indicatrix that contains the OA
What is a circular section?
A section through the indicatrix that is at 90* to the OA
What is a random section?
A section through the indicatrix that produces an ellipse with axes ne’ and nw. It DOES NOT include the OA.
uniaxial (+) means that n(e)is _____ than n(o)
Greater
(where z = c-axis = Optic Axis) –> produces oblate sphere
