13) Diffraction & Interference Flashcards

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1
Q

Light passing through each slit spreads out. What is the name for this effect?

A

Diffraction.

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2
Q

State what is meant by monochromatic.

A

Single wavelength.

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3
Q

State what is meant by coherent.

A

Waves have constant phase difference and the same

frequency.

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4
Q

State one safety precaution that should be taken while using a laser.

A

do not look into laser, wear goggles.

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5
Q

In the double slit experiment, the laser is replaced by another laser emitting visible light with a shorter wavelength. State and explain how this will affect the spacing of the maxima on the screen.

A
  • Maxima closer together.

- Spacing is proportional to wavelength and D and s are constant therefore as λ decreases so ω decreases.

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6
Q

State and explain what happens to the value of angle θ for the first order beam if the wavelength of the monochromatic light decreases.

A

angle θ gets smaller because path difference gets smaller.

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7
Q

State two ways in which the appearance of the fringes would change if the slit was made narrower.

A
  • wider separation.

- lower intensity.

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8
Q

In the double slit experiment, explain how the use of the single slit makes the light from the two slits sufficiently coherent for fringes to be observed.

A
  • Single slit acts as a point light to both slits.

- The path lengths between the single slit and the double slits are the same.

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9
Q

Explain how the bright fringes are formed in Young’s double slit experiment.

A

-Superposition of waves from two slits.
-Diffraction patterns from both slits overlap and interfere
constructively.
-Constructive interference at the bright fringes.
-Waves from each slit meet in phase.

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10
Q

Explain how the pattern produced on the screen by an electron diffraction tube supports the idea that the electron beam is behaving as a wave rather than as a stream of particles.

A
  • Wave property is shown by diffraction.
  • Graphite causes electron to spread out and travel in particular directions.
  • Bright rings occur where waves interfere constructively.
  • Particle behaviour would only produce a spot of light.
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11
Q

Explain why the signal strength falls to a minimum between two points in a double slit experiment.

A
  • path difference for two waves.
  • gives rise to a phase difference.
  • Destructive interference occurs.
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