Diffraction and interference - slits, gratings, and holes

 

1 Diffraction of water waves (barriers and gaps)

1 The end of a barrier acts as the source of new waves. (What principle is involved).

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2 What is the bending of waves into a shadow region called?

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3 What part of the process do many texts leave out of the diagram showing diffraction around a barrier?

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4 Under what conditions do interference bands appear in a single slit diffraction pattern?

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5 Who was the first to report interference fringes in the edge of a shadow?

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2 The two source interference pattern

1 How (briefly) may regular ripples be made in a shallow tank?

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2 What exactly is happening on a nodal line in terms of the two wave sets?

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3 Why are there very dark spots along lines of reinforcement in Ripple tank photographs?

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4 What effect do the following have on the separation of nodal lines?

a Increasing the wavelength. ....................................................................................................

b Increasing the source separation. ....................................................................................................

c Increasing the distance from the sources. ....................................................................................................

 

3 Wavelength measurements using the two source interference pattern

1 What exactly are the variables .... l, d, x and l .... in the equation .... l = dx / l ...?

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2 Why is it not necessary to measure x and l inside the eye, when using two slits to estimate the wavelength of light?

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3 What is the path difference for waves on the first line of reinforcement?

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4 What shape do the lines of reinforcement have; near the sources and far from the sources?

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5 What is the size relationship between red, green and blue patterns ...... and why are white-light fringes colored?

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6 What effect does the single slit diffraction pattern have on the fringes seen with a double slit?

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7 What would be the advantages of using laser light for a double slit demonstration in a lecture hall?

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4 Diffraction gratings

1 Why do we not observe single slit diffraction with a diffraction grating?

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2 What are the differences and similarities between fringes made with a double slit and a grating?

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3 What is a 'first order' grating?

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4 What is the grating formula?

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5 What could you use to make diffraction gratings for sound, and for X-rays?

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5 Interference in thin films

1 What phase changes occur at closed and open boundaries?

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2 For what thickness of soap (water) film does no reflection occur?

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3 What substance is coated on lenses to reduce unwanted reflection (blooming).

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4 What are Newton's rings, and how are they used to test for optical flatness?

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6 Rayleigh's Criterion

1 What does the diffraction pattern of a small hole look like?

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2 What is the Airy disc?

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3 Interpret the symbols in the equation x'/L' = 1.22 l/d with a diagram.

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4 What is meant by the resolving power of an atronomical telescope, and how is it calculated?

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7 Scattering

1 Small objects scatter waves in approximately circular (spherical) patterns. What is meant by small?

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2 Why is the sky blue (dark blue in Tibet)?

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3 Why is sound (not light) our 'early warning system'?

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4 Can laser light be scattered?

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8* Diffraction in the atmosphere

1 How exactly can the average droplet size be estimated from the size of a diffraction halo?

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