# Find the wavelength of light used if the 2nd order minimum is located 21cm from the central maximum on a screen 90cm away. The separation?

between the double slits is 6 x 10^-6 m.

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- NCSLv 74 weeks agoFavorite Answer
Treating 90 cm as "distant"

y ≈ (n+½)λD / d

0.21 m ≈ (2+½)*λ*0.90m / 6e-6m

λ ≈ 5.6e-7 m = 560 nm

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