Diffraction path difference

What happens during diffraction?

When waves pass through two slits, they create two sets of waves which can interfere with each other.
It creates a pattern of alternating bright and dark fringes on the screen.
The central bright fringe is the brightest, and the fringes get less bright as you move away from the centre.
The bright fringes are equally spaced.

They interfere constructively when the peaks of both of the waves line up.
- That happens when the phase difference between the two waves is a multiple of 2\pi, and when the path difference between the two waves is a multiple of one wavelength (\lambda).
- The constructive interference creates the bright fringes.
They interfere destructively when the peaks of one wave line up with the troughs of the other wave
- That happens when the phase difference between the two waves is not a multiple of 2\pi, and when the path difference between the two waves is not a multiple of one wavelength (\lambda).
- It will produce dark fringes on the screen.
The further away the fringe is from the centre, the larger the path difference is between the waves, and so the fringes will be less bright (for constructive interference).

Question	Answer
What is the path difference condition for constructive interference in diffraction?	The path difference between the two waves must be a multiple of one wavelength (\lambda), and the phase difference must be a multiple of 2\pi.
What is the path difference condition for destructive interference in diffraction?	The path difference between the two waves must not be a multiple of one wavelength (\lambda), and the phase difference must not be a multiple of 2\pi.
What is observed when waves diffract through two slits?	They create two sets of waves which interfere, producing a pattern of alternating bright and dark fringes on a screen.
Which fringe is the brightest in a two-slit diffraction pattern?	The central bright fringe is the brightest.
What happens to the brightness of the bright fringes as you move away from the centre?	The fringes get less bright as you move away from the centre.
Are the bright fringes in a two-slit diffraction pattern equally spaced?	Yes, the bright fringes are equally spaced.
How does the path difference relate to the fringe distance from the centre?	The further away the fringe is from the centre, the larger the path difference is between the waves.
Why do fringes become less bright further from the centre?	The larger path difference for fringes further from the centre causes the fringes to be less bright, even during constructive interference.