ch. 17 Flashcards
There is a reflection at the boundary between two materials if there is a change of __________ at the boundary.
speed of the light in the materials
The colors of a soap bubble or oil slick are due to __________
thin-film interference
As the number of slits of a diffraction grating increases, the bright fringes observed on the viewing screen _________
get narrower and brighter
In single-slit diffraction, what happens to the dark fringes if the slit gets wider?
they get closer together
what is diffraction
it is the spreading of a wave after it passes through an aperture
what happens when light waves travel through an object with a higher index of refraction
the speed slows down and the wavelength shortens but the frequency does not change
what happens when two light waves overlap
they can interfere constructively or destructively
How does the double spilt experiment work
a light beam is shot at two slits, this produces two light sources that can overlap and interfere with eachother which creates patterns on a screen behind them
when does constructive interference occur in a double slit experiment
when r1 and r1 pathlengths differ by a whole number of wavelengths, they constrcutively interfere and create brighter bands
when does destructive interference occur
when r1 and r2 differ by a whole number of wavelengths and a half they interfere destructively and appear dark
what is an interference fringe
it is a series of alternating bright and dark bands of light
what is the central maximum
it is where m=0 and it is the brightest fringe
in double spilt interference, what is the spacing between the bright lines
it is equally spilt
what is diffraction grating
it creates multiple sources of waves that interfere with each other
can you use small angle approximation with diffraction grating
no
in comparison to the birght fringes in doubke spilt, what is the pattern in the size of the fringes in diffraction grating
they are much narrower
in diffraction grating, what happens as the number of slits increases
the fringes get brighter and narrower
how is spectroscopy used in diffraction
atomic elements emit certain wavelengths which can affect the angles of lines
what is thin film interference
the interference of light waves reflected from two boundaries of a thin film
when is light partially reflected from a boundary?
when the two boundaries have different indices of refraction
what is a phase change
when a light wave moves from a medium with a lower index of refraction to a higher index of refraction, the reflected wave is inverted and this adds an extra half-wavelength to the distance the wave travels
when does light undergo a phase change
if it reflects from a boundary where the index of refraction increases
when will two reflective waves interfere constructively
when their crests are in phase and it causes a strong reflection
when will two reflected waves interfere destructively
when their crests are out of phase and they reflect weakly
if n1<n2, is there a phase shift in thin film
yes
if there is 1 phase shift, what happens to the formula 2t=m (wavelength)/n
the conditions for a constructive wave becoem destructive
if there is 0 or two times that n1<n2, what happens to the formula 2t=m (wavelength)/n
it means the conditions for constructive remain constructive
what is single slit diffraction characterized by
the light pattern has a central maximum and a series of weaker secondary maxima and dark fringes
the central maximum is much brighter than the secondary
what is huygen’s principle
each point on a wave front is the source of a spherical wavelet that spreads out at the wave speed
at a later time, the shape of the wave front is the curve that is tangent to all the wavelets
why is there a central maxima
the paths of several wavelets travel straight ahead and are in phase so they add constructively at theta= 0
every point on the wave front can be paired with another that is
a/2 distance away
for single-slit diffraction, the smaller the openig a wave squeezes through, the _______ it spreads out onto the other side
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