The light intensity vs. position graph of a double-slit experiment is shown below. The graph was made with helium-neon laser light of wavelength 630 nm shined through two very narrow slits separated by a small distance. The slits were 2.0 meters away from the probe. What is the path-length difference (from the two slits to the screen) when the probe is at position 9.0 mm, in nm? Your answer needs to have 2 significant figures, including the negative sign in your answer if needed. Do not include the positive sign if the answer is positive. No unit is needed in your answer, it is already given in the question statement.

The light intensity vs. position graph of a double-slit experiment is shown below. The graph was made with helium-neon laser light of wavelength 630 nm shined through two very narrow slits separated by a small distance. The slits were 2.0 meters away from the probe. What is the path-length difference (from the two slits to the screen) when the probe is at position 9.0 mm, in nm? Your answer needs to have 2 significant figures, including the negative sign in your answer if needed. Do not include the positive sign if the answer is positive. No unit is needed in your answer, it is already given in the question statement.