A uniform metal meter-stick is balanced with a 1.0 kg rock attached to the left end of the stick. If the support is located 0.25
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Answer:
(a) d = 1960nm
(b) The slit should be decreased.
(c) Δd = 360nm.
Explanation:
The double-slit interference is given by the following equation:
(1)
<em>where d: is the distance between slits, Θ: is the angle between the path of the light and the screen, m: is the order of the interference and λ: is the wavelength of the light. </em>
(a) To determine the least wavelength in the visible range in the third-order we need first to find the distance between slits, using equation (1) for a fourth-order:
Now, we can find the least wavelength in the visible range in the third-order:
So, the least wavelength in the visible range (400nm - 700nm) in the third-order is 653nm.
(b) To eliminate all of the visible light in the fourth-order maximum <u>means that the wavelength must be smaller than 400nm</u>, and hence the slit separation should be decreased <u>since they are proportional to each other</u> (see equation (1)).
(c) The distance between slits needed to eliminate all of the visible light in the fourth-order maximum, with λ = 400 nm as limit value, is:
Therefore the least change in separation needed is equal to the initial distance calculated for 490nm and the final distance calculated for 400nm:
I hope it helps you!