Midterm I Flashcards
What are the two types of radiation based on radiation effect?
Ionizing Radition - particle and EM radiation with ultraviolet or shorter wavelengths
Non-Ionizing Radiations - visible light and lower wavelengths, sound and ultrasound
What is the formula for attenuation of radiation?
J = J0⋅e−μx
Where J is attenuated radiation, J<strong>0</strong>is initial radiation, μ is a constant for the attenuating material and x is the thickness of the material.
What is the difference between transverse and longitudinal waves?
**Transverse **- wave oscillates perpendicular to its direction of travel
Longitudinal - wave oscillates in the same direction as its travel
What are the two types of waves categorized by source?
Mechanical - elastic disturbance through elastic medium
Electromagnetic - electronic disturbance propagating through space (vacuum)
What are the 3 types of waves according to their dimension of propagation?
one-dimensional - rope
surface - pond ripples
spatial - sound
What does the Huygens-Fresnel principle state?
Every point in a wavefront is a source of further waves
Describe the image in the retina.
Real, diminished, inverted
What is Wien’s Displacement Law?
the wavelength distribution of thermal radiation from a black body at any temperature has essentially the same shape as the distribution at any other temperature, except that each wavelength is displaced on the graph
What is Snell’s Law, both as it relates to wave velocity and index of refraction?
Snell’s law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media, or equivalent to the reciprocal of the ratio of the indices of refraction:
- Can be rearranged as V1/sin θ1 = V2/sin θ<strong>2</strong> or as
n2 x sin θ2 = n1 x sin θ1
What is the trigonometric mnemonic for what sine, cosine and tangent mean?
Explain it.
SOH CAH TOA
Sine = Opposite/Hypotenuse
Cosine = Adjacent/Hypotenuse
Tangent = Opposite/Adjacent
What is the critical angle?
Why does it exist?
The **critical angle **is the angle of incidence at which the angle of refraction is 90 degrees (and thus the refracted ray travels along the interface of the 2 media).
- Critical angles exist because when light moves from a slow medium to a fast medium, its angle of refraction will always be greater than its angle of incidence.
How does one find the critical angle, past which total internal reflection will occur, when shining light from a slow to a fast medium?
ni× sin θi = nr
Same as Snell’s law, but sin θr = 1 (and is therefore left out) because the angle of refraction (θr) is 90 degrees.
According to Abbe’s formula, how is the resolution limit of a microscope decreased?
by decreasing wavelength of illuminating light and increasing aperature angle of the objective lens
How will decreasing the refractive index affect its optical power? focal length?
Will decrease optical power and increase focal length
What are some of the manifestations of light’s wave nature and when do they occur?
Light acts as a wave during propagation:
- diffraction
- interference
- polarization
What are some of the manifestations of light’s particle nature and when do they occur?
Light acts as a particle during interactions:
- photoelectric effect
- refraction
- excitation/ionization
- Compton scatter
- pair production
What is the photoelectric effect?
the effect of electron emission from many metals that is caused when light is shined upon them
What are the particle vs. non particle radiations?
Alpha radiation and Beta radiation are particle radiations.
Gamma radiation is non-particle.
Describe Alpha radiation.
An atom gives off 2 protons and 2 neutrons, releasing a Helium atom.
- the atom therefore loses 4 AMUs and 2 atomic numbers
Describe the two types of Beta radiation.
Positron Emission (B+ decay)
- a proton emits its positive charge as a positron, but keeps its mass, becoming a neutron
- atom keeps its mass but loses 1 atomic number
Electron Emission (B- decay)
- a neutron loses an electron and becomes a proton
- atom keeps its mass and gains 1 atomic number
Describe Gamma radiation.
Unlike alpha and beta, there is no major change in subatomic constituents.
Neutrons and protons simply bundle tighter together in the nucleus, increasing the energy state of the atom and emitting radiation.
What is optical power?
What is is measured in?
Describe its relationship to focal length.
Optical power is the light ray converging power of a lens.
It is measured in diopters or 1/m.
It is inversely proportional to focal length.
(A “stronger” lens of greater optical power converges rays a a closer distance or shorter focal length.)
What is the lens makers equation?
D = (n12 - 1)(1/R1 + 1/R2)
What is the lens equation?
1/f = 1/i + 1/o
What is the equation which relates image size and distance to object size and focal length?
O/f = (O + I)/i
How is magnification determined?
Image size or distance divided by object size or distance.
M = I/O = i/o
What does a negative image distance indicate?
a virtual image on the same side of the lens as the object
What does a negative image size indicate?
an upright, virtual image
How is absolute refractive index determined?
n1= C/C1
abs. refractive index = speed of light in vacuum over speed of light in medium
How can the critical angle be determined?
by setting the incident angle at 90 degrees
How can the angle of total internal reflection be determined?
by setting the refracted angle to 90 degrees
What is Fermat’s principle?
Rather than taking the shortest distance between two points, light takes the route which would take the least time.
In other words, it travels as long as possible in the less optically dense medium.
How can electron volts be determined from wavelength?
- convert wavelength from nm to m
- use E = hf = h(c/λ) to get Joules
- convert to eV with 1 eV = 1.6x10-19 J
How can λ causing photochemical effect be determined if given required energy in kJ/mol?
- convert to J/mol
- divide by avogadro’s number to get J
- use E = h * (C/λ) to find wavelength
