Wavelength measurements using a two source interference pattern

Questions

1 The wavelength l = dx / l ... where d, x and l have their usual meanings.

Draw lines the diagram with a ruler and mark the lengths d, x and l.

 

2 Why is it not necessary to measure x and l inside the eye (as above), when looking through two slits to estimate the wavelength of light?

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3 Why is the central line, marked on the diagram of the eye above, always a line of reinforcement in the inerference pattern?

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4 In which part of a two slit interference pattern can nodal lines not be considered to be straight lines?

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5 When a double slit interference pattern is viewed through two slits a series of fringes are seen. Which pattern is larger, red or blue?

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7 Why are white-light fringes colored?

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8 What type of light source should be used to project interference fringes on to a screen in a lecture hall?

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