12 - Waves 2 Flashcards
(31 cards)
What happens when two waves pass through each other?
.Resultant displacement is the sum.
.Add together.
.Superpose - resultant wave with increased/decreased amplitude.
How does friction effect a wave?
Wave energy not the speed.
What are the conditions for superposition to work?
.Must be same type.
.Medium must behave linearly.
Define coherence.
Waves from both sources have the same frequency and phase difference is constant. Observable fixed interference.
What produces coherent light?
Lasers, not filament bulbs.
What is the phase difference for waves in phase?
360 or 2pi.
What is the phase difference for waves in antiphase?
180 or pi.
What is the equation for phase difference?
x/λ x 360.
Define path difference.
The difference in distance travelled by two waves in λ.
What is the path difference in constructive interference?
nλ.
What is the path difference in destructive interference?
n/2 λ.
What is the double slit equation?
λ = ax/D.
How do you do the double slit experiment?
.Place with filter and single slit.
.Place through double slit.
.Interference patterns.
What does the a stand for?
Split separation.
What does the D stand for?
Distance to the screen.
What does the x stand for?
Distance between fringes.
How does the diffraction grating differ from the double slit?
.More slits enhances the interference pattern.
.More light beams contribute to the pattern.
.Brighter/narrower bright fringes.
.Darker/more pronounced dark fringes.
.More accurate measurements.
What are the four diffraction grating equations?
.x2 - x1 = nλ.
.tanθ = h/d.
.dsinθ = nλ.
.N = 1/d.
How do you work out wavelength using a diffraction grating?
1.Measure slit width. 2.Measure distance of grating from wall.
3.Turn on laser.
4.Mark the fringes.
5.Measure each fringe.
6.Work out mean for h.
7.Work out θ using tan^-1 h/d.
8.Plot dsinθ against n.
9.Work out wavelength.
How does a diffraction grating differ to the double slit experiment?
Brighter/ more clear fringes so better more accurate results.
What happens when you increase slit separation?
Pattern decreases.
What happens when you increase wavelength.
Size increases of pattern - less bright.
How does a standing wave form?
Wave reflected and superposes - interference causes nodes/antinodes.
What happens at a node?
0 displacement.
