Topic 13 Flashcards
What is the speed of light?
c = 3 x 108 m/s
When would geometric optics be used?
If the wavelengths are shorter than the sizes of the tools
If the energies used are negligable
Give the concepts of the light ray
Crossing light waves don’t influence one another.
Light travels in straight lines
Refraction occurs on the border of different media
Light paths are reversible.
What are the rules of reflection?
On a smooth surface:
Incident and reflected ray have the same angle
Angle of refracted ray depends on the medium
Give the equation of Snell’s Law
What does Snell’s Law describe?
Both Rays and the normal are in the same plane during refraction
What is the index of refraction?
Measurement of how the medium refracts light, dependent on the wavelength
What is the relative index of refraction?
n2,1
The index of refraction of medium 1 to medium 2
What is the absolute inex of refraction?
The index of refraction calculated with the speed of light differences in two different media
What is total reflection?
No incident rays enter the second medium.
Angle of refraction is 90°
Incident angle is known as the critical angle
No loss of energy
What is a light pipe?
Small pipe where light is totally reflected to allow travel over long distances without attenuation.
Describe the use of fiber optics.
Many light pipes are needed to transmit an image
Smaller radius of pipe → Better image
Used for endoscopies, e.g Urinary bladder
Describe the light path in a planparallel slab
If the medium on both size is the the same, the ray angle is unchanged.
Distance of ray entry/exit increases proportionally to the slab thickness.
Describe refraction in a prism.
Prism walls are at an angle:
Light will bend accodring to Snell’s Law
Describe dispersion of light
Index of refraction dependednt on wavelength
If an incident ray has several wavelengths, they will be seperated.
