Monochromatic light with wavelength 685 nm is incident on a pair of slits, and a
ID: 2055235 • Letter: M
Question
Monochromatic light with wavelength 685 nm is incident on a pair of slits, and an interference pattern forms on a screen some distance away. The slits are arranged side by side. In the following questions, you will be asked to compare the pathlength difference for light traveling for the two slits to a given part of the pattern. For example, if you were asked how much farther light from the left slit travels than light from the right slit on its way to the m = 1 maximum on the right side of the pattern, you would compare the two dashed lines in this figure:
(a) Consider the m = 5 maximum on the right side of the central maximum. How much farther does light which passes through the left slit travel on the way from the slit to this maximum compared to light which passes through the right slit?
(b) Consider the m = 4 minimum on the right side of the central maximum. How much farther does light which passes through the left slit travel on the way from the slit to this minimum compared to light which passes through the right slit?
Explanation / Answer
Part A)
If you have a maxima, no matter which one, you have constructive interference. To have that situation , the light from the farther slit will travel one wavelength more than the light from the closer slit. So the answer is one wavelength more. ( more)
Since is given as 685 nm, than the answer is 685 nm
Part B)
If you have a minima, no matter which one, you have destructive interference. To have that situation , the light from the farther slit will travel one half wavelength more than the light from the closer slit. So the answer is one half wavelength more. (/2 more)
Since = 685 nm, the answer is 342.5 nm