Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
5 Cards in this Set
- Front
- Back
|
Young's Double Slit Experiment
|
1) monochromatic red light source behind a single slit in a black obstacle, X
light passing through this split diffracts until it reaches another obstacle Y, where there are two parallel narrow slits 2) light from these slits is coherent (starts at same source and is in phase at double slit) 3) diffracts again until it reaches a screen 4) centre of pattern (O), B, D, F = constructive A, C, E, G = destructive 5) fringe width using red light is greater than with green light, red light has a longer wavelength γ/d = sinθ γ is wavelength, a is slit spacing, x is fringe width, D is distance to screen from double slits |
|
|
Young's Double Slit Experiment with Microwaves
|
1) microwave generator placed 20cm in front of a metal sheet with 2 slits about 5cm apart. a microwave detector can be moved across the wave pattern to find the maximum and minimum.
|
|
|
Diffraction Grating - Multiple Slits
|
difficult to determine wavelengths from double slit method, too blurred so measuring fringe width is difficult
use multiple slits, gratings can be made with 500 or more slits per mm angle of diffraction is such that each ray travels exactly one wavelength further than the ray above it (for this angle all rays will be in phase, reinforce for maximum intensity) lambda = d sin theta |
|
|
Measuring wavelength of light using a diffraction grating
|
diffraction grating placed in parallel beam of monochromatic light from a sodium lamp
angle between light passed through the grating and the diffracted beam is measured number of angles where light can be seen (called maxima) when path difference between light from adjacent slits is 2γ,3γ,4γ number of pattern, n, on either side of central maximum is known as the order γ/d = sinθ → nγ = d sinθ |
|
|
de broglie diffraction
|
used to determine atomic spacing and to prove particles (e.g. electrons) can act as waves - must exhibit a wave property/characteristic like diffraction or interference
electrons can be diffracted: electrons from an electron gun accelerated through a vacuum towards a layer of polycrystalline graphite (wavelengths of electrons smaller than light so diffraction gratings are not suitable - atomic spacing of graphite is used) -graphite atoms not regimented therefore electron diffraction pattern is circular lambda = h/mv lambda is wavelength, h is planck's constant, m is rest mass of electron, v is speed of electron |
