double slit experiment Flashcards
Explain what is meant by a constant phase difference.
- same frequency
- same wavelength
Explain what is meant by the term ‘coherent’.
- constant phase difference
- same frequency
How do we ensure coherence for a non-coherent light source?
colour filter - filter out to one frequency
single slit - behaves as single source of light to get a constant phase difference
State the relationship between amplitude and intensity.
higher the amplitude, highter the intensity
What are the centre of bright fringes called & how are they produced?
- maxima
- produced by constructive interference
What are the centre of dark fringes called & how are they produced?
- minima
- produced by destructive interference
When are maximas formed?
when:
- path difference is an even number of 1/2 λ
- phase difference is an even multiple of π
When are minimas formed?
when:
- path difference is an odd number of 1/2 λ
- phase difference is an odd multiple of π
Explain how a maximum is formed at a point on the screen in the double-slit experiment.
a maximum is formed when two waves superpose to produce constructive interference
→ waves must arrive in phase (phase diff of even multiple of π)
→ (if initially in phase), they will arrive in phase if path difference is even number of 1/2 λ
→ this results in maximum possible amplitude, meaning that the stripe on the screen has maximum intensity.
Explain how a minimum is formed at a point on the screen in the double-slit experiment.
a minimum is formed when two waves superpose to produce destructive interference
→ waves must arrive in antiphase (phase diff of odd number of π)
→ arrives in antiphase if path difference is an odd multiple of 1/2 λ
→ results in minimum possible amplitude, meaning that the stripe on the screen has minimum intensity.
What happens to fringe spacing as distance to screen decreases?
decreases
Why is a central white fringe produced when white light is used in a double slit experiment?
All the different wavelengths produce a central fringe, and these overlap to produce white light.
Describe the fringe patten for white light.
- central white fringe
- rainbow fringes on either side
- from blue to red as we progress outwards from the centre