Diffraction - AP Physics 2

Destructive interference occurs when waves combine to produce a smaller amplitude. This occurs when waves arrive out of phase with each other.

$d \sin \theta = m \lambda$ where $m$ is an integer. This gives bright fringe positions in the interference pattern.

Increasing slit width decreases the extent of diffraction. Wider slits concentrate more energy in the forward direction.

The zero-order maximum is the brightest and occurs directly opposite the source. This is the undiffracted beam with $m = 0$ in the grating equation.

Coherence is necessary for producing clear and stable diffraction patterns. Coherent sources maintain constant phase relationships for interference.

Diffraction is bending around obstacles; refraction is bending through different media. Diffraction involves wave spreading; refraction involves speed changes.

A longer wavelength results in a wider diffraction pattern. This follows from the inverse relationship in diffraction formulas.

Decreasing slit width increases the width of the central maximum. Smaller slits spread light over larger angular ranges.

Longer wavelengths produce lower-order maxima at larger angles. Longer wavelengths satisfy the grating equation at larger angles.

$\Delta r = d \sin \theta$. This represents the extra distance traveled by one wave.

Higher frequency waves diffract less than lower frequency waves. Higher frequency means shorter wavelength and less diffraction.

Order refers to the sequence number of maxima in a diffraction pattern. Order $m$ counts the number of wavelengths in path difference.

$\lambda$ is the wavelength of the incident wave. This determines the scale of the diffraction pattern features.

The wavelength of the incident wave. Wavelength directly determines the angular scale of the pattern.

Fringe spacing decreases as slit separation increases. Closer slits create wider-spaced interference fringes.

Narrower slits produce wider diffraction patterns. Smaller openings cause greater spreading due to wave properties.

The wavelength of the wave relative to the size of the obstacle or opening. Comparable sizes produce the strongest diffraction effects.

Longer wavelengths produce wider diffraction patterns. Greater wavelength means more bending around apertures.

Increases the sharpness and brightness of maxima. More slits create narrower, more intense diffraction peaks.

$\Delta \theta = \frac{2 \lambda}{a}$. This spans from first minimum to first minimum on opposite sides.

Increases the resolution of the diffraction pattern. More grooves per unit length create sharper spectral lines.

$a , \sin \theta = \lambda$. This is where $m = 1$ in the general minima formula.

Larger slit separation results in smaller diffraction angles. Larger $d$ requires smaller $\sin \theta$ for the same wavelength.

$d \sin \theta = m \lambda$ where $m$ is an integer. This gives bright fringe positions in the interference pattern.

The diffraction limit is the smallest angular separation resolved by a lens or aperture. This sets the minimum resolvable detail size in optical systems.

Multiple slits produce sharper and more numerous maxima. Multiple slits create additional interference that sharpens the pattern.

The principle that the resultant displacement is the sum of individual displacements. This allows calculation of net wave amplitude at any point.

$a , \sin \theta = m \lambda$ where $m$ is an integer (except 0). This gives destructive interference positions where intensity is minimum.

$d$ is the distance between the centers of the two slits. This spacing determines the fringe separation in the pattern.