Flashcards in Chapter 17 Deck (31):
what is diffraction?
waves after passing through an opening, spread out and fill the space behind the opening
what is light?
the nature of light is...
light is a wave and light is a beam of tiny particles, blowing around like the wind
what is the speed of light?
v = c = 3.0*10^8
v = fλ
what is the visible light spectrum?
400nm - 450nm = violet light
450nm - 500nm = blue light
500nm - 570nm = green light
570nm - 590nm = yellow light
590nm - 610nm = orange light
610nm - 700nm = red light
what ere the two models of light?
1. The Ray Model: under some circumstances, light acts like particles travelling in a straight line (large openings/ acts on beam)
2. The Wave Model: Under other circumstances, light acts like a wave (small openings/ diffraction)
Interference pattern can be observed from two slits?
bright and dark lines (or fringes)
Δy = fringe spacing
what is path difference?
Δr is path difference
what is phase difference?
Δφ = 2piΔr/λ
If Δr = λ, 2λ, 3λ, 4λ,..... then this is ?
This is constructive interference = mλ
If Δr = λ/2, 3λ/2, 5λ/2,.... then this is?
This is destructive Interference = (m+ 1/2)λ
How do we solve for bright fringes (double-slit interference)?
Δr = dsinθ = mλ
tanθ = y/L
how do we find the position of bright fringes (double-slit interference)?
y = mλL/d
m = 0, 1, 2, 3,.....
how do we find the position of dark fringes (double-slit interference)?
y' = (m + 1/2)λL/d
m = 0, 1, 2, 3,....
what is a diffraction grating?
it is a multi-slit device, the waves emerge from each slit in phase
how do we find the angles of bright fringes due to a diffraction grating with slits distance d apart?
dsinθ = mλ m= 0, 1, 2, 3,.....
- solve for sinθ; if sinθ
what is spectroscopy?
the science of measuring the wavelengths of atomic and molecular emissions
what is single-slit diffraction?
Is diffraction through a tall narrow slit with a slit width of (a)
what is Huygen's principle?
1. each point on a wave front is the source of a spherical wavelet(mini wave that is spherical) that spreads out at the wave speed
2. at a later time, the shape of the wave front is the curve that is tangent to all the wavelets
how can we find the angles (in radians) of dark fringes in a single-slit diffraction with a slit width of a?
θp = p(λ/a) p= 1, 2, 3,...
y = pλL/a p= 1, 2, 3,... (position of dark fringes for single-slit diffraction)
How do you find the width of the central maximum for a single-slit diffraction grating?
w = 2λL/a
what is circular-aperture diffraction?
light diffracts and generates a circular diffraction pattern
how do we find the first minimum intensity for a circular-aperture diffraction?
θ1 = 1.22λ/D
w = 2y1 = 2Ltanθ1 = 2.44λL/D (width of central maximum for diffraction from a circular aperture of diameter D)
what does resolve mean?
separate out details of an object that is being viewed
what is thin-film interference?
1. incidence wave is transmitted through the thin film and the glass
2. Part of the incidence wave reflects from the first surface
3. Part of the transmitted wave reflects from the second surface
4. The two reflected waves overlap and interfere
Thin film interference is due to path difference, what are these path differences?
actual: path differences in the distances travelled (just like in double and single slit experiments)
effective: path differences due to passage through different media and phase inversion at a boundary
Index of refraction is?
n = c(speed of light)/v(speed of light in the medium)
c = n1v1 = n2v2
n1λ1 = n2λ2
frequency does not change when you transition from different mediums
How do we solve thin-film interference problems?
1. draw the path of light rays through the film
2. determine the phase shifts due to reflection
3. Calculate the path difference due to the extra distance travelled by the rays crossing the film
4. Don't forget to take into account the index of refraction of the film
0 and 2 phase inversions?
constructive interference = 2t = mλ/nfilm
destructive interference = 2t = (m+1/2)λ/nfilm
1 phase inversions?
always destructive interference
2t = mλ/nfilm or 2t = 1/2λ/nfilm
If the ray reflects from a high to low medium that means that there is?
a phase inversion