# Physics - Superposition

> Source: https://ollybritton.com/notes/a-level/physics/topics/superposition/ · Updated: 2021-05-25 · Tags: school, waves, year-1

## See Also
- [Physics - Waves](https://ollybritton.com/notes/a-level/physics/topics/waves/)
- [Physics - Standing Waves](https://ollybritton.com/notes/a-level/physics/topics/standing-waves/)

## Flashcards
##### At what phase differences does total constructive superposition occur??
$$
0, 2\pi, 4\pi, 6\pi, 8\pi, ...
$$

##### At what phase differences does total destructive superposition occur??
$$
\pi, 3\pi, 5\pi, 7\pi, 9\pi
$$

##### What requirement other than phase difference is there for total destructive superposition??
Both waves need to have the same amplitude.

### 2021-05-27
##### What does it mean for two wave sources to be coherent??
They have the same frequency.

##### What does two wave sources being coherent mean can happen??
They can form a stable interference pattern.

##### What is "path difference"??
The difference in distance that two different waves have travelled from their sources.

##### What is a "central maxima"??
The middle part of an interference pattern with the largest amplitude.

##### What is the "1st order maxima" in an interference pattern??
The second largest part of an interference pattern.

##### What is the "1st order minima" in an interference pattern??
The first region of total destructive interference.

##### What is the phase difference for the 2nd order maxima in an interference pattern??
$$
4\pi
$$

##### What is the path difference for the 2nd order maxima in an interference pattern??
$$
2\lambda
$$

##### What is the phase difference for the 2nd order minima in an interference pattern??
$$
3\pi
$$

##### What is the path difference for the 2nd order minima in an interference pattern??
$$
\frac{3\pi}{2}
$$

##### What does it mean for integer multiples of the path difference in an interference pattern??
They form a maxima.

##### What does it mean for even multiples of $\pi$ for the phase difference in an interference pattern??
They form a maxima.

##### What does it mean for half-multiples of the path difference in an interference pattern??
They form a minima.

##### What does it mean for odd multiples of $\pi$ for the phase difference in an interference pattern??
They form a minima.

### 2021-06-08
##### What's one way of getting a set of coherent waves experimentally??
* Use a single light source
* Pass through one slit
* Have it diffract through two more slits

##### How can you get two coherent longitudinal waves??
Use two speakers connected to the same signal generator.

##### What's the formula for working out the wavelength $\lambda$ from a interference pattern given the slit seperation $a$, the fringe spacing $x$ and the slit-to-screen distance $D$??
$$
\lambda = \frac{ax}{D}
$$

##### $$\lambda = \frac{ax}{D}$$ What assumption do you make for this equation to work??
That the slit-to-screen distance $D$ is much greater than the slit seperation $a$.

### 2021-06-17
##### What is true in terms of phase difference for two coherent waves??
They will have a constant phase difference.

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