double slit experiment Flashcards

1
Q

Explain what is meant by a constant phase difference.

A
  • same frequency
  • same wavelength
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2
Q

Explain what is meant by the term ‘coherent’.

A
  • constant phase difference
  • same frequency
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3
Q

How do we ensure coherence for a non-coherent light source?

A

colour filter - filter out to one frequency
single slit - behaves as single source of light to get a constant phase difference

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4
Q

State the relationship between amplitude and intensity.

A

higher the amplitude, highter the intensity

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5
Q

What are the centre of bright fringes called & how are they produced?

A
  • maxima
  • produced by constructive interference
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6
Q

What are the centre of dark fringes called & how are they produced?

A
  • minima
  • produced by destructive interference
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7
Q

When are maximas formed?

A

when:
- path difference is an even number of 1/2 λ
- phase difference is an even multiple of π

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8
Q

When are minimas formed?

A

when:
- path difference is an odd number of 1/2 λ
- phase difference is an odd multiple of π

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9
Q

Explain how a maximum is formed at a point on the screen in the double-slit experiment.

A

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.

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10
Q

Explain how a minimum is formed at a point on the screen in the double-slit experiment.

A

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.

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11
Q

What happens to fringe spacing as distance to screen decreases?

A

decreases

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12
Q

Why is a central white fringe produced when white light is used in a double slit experiment?

A

All the different wavelengths produce a central fringe, and these overlap to produce white light.

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13
Q

Describe the fringe patten for white light.

A
  • central white fringe
  • rainbow fringes on either side
  • from blue to red as we progress outwards from the centre
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