OPTICS + PARTICLE STUFF Flashcards
(28 cards)
What is the visible light section of spectrum?
380nm - 750nm
What are the two parts of optics?
Geometric (for objects larger than wavelength, propagation is through geometrical objects) Wave optics (for objects around size of wavelength)
What does Huygen’s principle state?
Every point on a wavefront may be considered as a source of a secondary wave that spreads out in the forward direction at speed equal to the speed of the wave.
What is the law of reflection?
Angle of incident ray is equal to angle of reflected ray
What are the refraction angles for n2> n1 and n1 > n2
For n2 > n1, a > b
For n1 > n2, b > a
When does total internal reflection occur?
When the incidence angle of ray a is greater than the critical angle (critical angle - angle at which ray will travel along 90 degrees) when trying to travel from a slower medium to a faster medium
Why does dispersion of light occur?
As different colours have slightly different index’s of refraction as index of refraction is a function of wavelength
What does the double-slit experiment exihibit
The diffraction of light
What does wave optics apply to?
Objects that have dimensions similar to wavelengths
What is thin film interference?
When a ray reaches a medium some of it reflects and some passes through the next medium boundary. At this boundary the ray reflects in the same manner as the first.
What possible phase shifts will occur in thin film interference?
If n2 > n1 then there is a pi phase shift (or wavelength/2) if n1 > n2 then no phase shift will occur.
What is polarised light and what occurs in non-polarised light?
Light that vibrates in only one place. Transverse waves can be polarised. In non-polarised light the direction of the electric field changes.
What are methods to polarise light?
By a polariser filter (only allows light through in one plane, typically vertical) or reflection.
What does Brewsters law convey?
Polarising angle for reflection with reference to the considered mediums.
What is particle nature of EM radiation?
The dualism of light - ability of em radiation to behave like a wave or a particle
What is quantised energy?
Energy is not continuous but is made up of discrete values (quantised)
What is a photon and its relation to photoelectric effect?
A particle of light.
An electron is ejected when a singular photon of sufficient energy strikes it.
How is energy and momentum of photon described?
E = hf (energy of photon is quantised) p = mc = h/wavelength
How is moving mass of a photon described?
E = hf =mc^2
==> m =hf/c^2 = h/(c.wavelength)
What is a black body?
An object that emits EM radiation of all wavelengths
What does Wein’s displacement law explain?
It explains black bodies peak wavelength relationship to temperature (objects emitt wavelength at their highest intensity)
What is compton scattering?
When a high energy photon collides with an electron. The scattered photon has a longer wavelength than the incident photon (wavelength change is proportional to scatter angle)
What is Braggs law and what does it use/how?
Allows to calculate distance between layers of atoms using x-ray diffraction. 1st x-ray hits an atom, 2nd x-ray comes at the same angle and strikes the atom below 1st. Braggs law: 2dsina = n(wavelength_max)
What is the Thomson model of an atom?
Electrons submerged in continuous positive matter
