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**1. Two slits are 0.153 mm apart. A mixture of red light (wavelength = 665 nm) and yellow-green light (wavelength = 565 nm) falls on the slits. A flat observation screen is located 2.17 m away. What is the distance on the screen between the third-order red fringe and the third-order yellow-green fringe?**

d= 0.153mm = 1.53 x 10^-3m

red wavelength= 665 nm = 6.65 x 10 ^-7 m

Yellow-green wavelength = 565 nm = 5.65 x 10^-7 m

x = 2.17m

m = 3

d= 0.153mm = 1.53 x 10^-3m

red wavelength= 665 nm = 6.65 x 10 ^-7 m

Yellow-green wavelength = 565 nm = 5.65 x 10^-7 m

x = 2.17m

m = 3

**2. Sin theta = m (wavelength/d)**

**3. red:**

Sin Theta = 3(6.65 x 10^-7) / (1.53 x 10^-3) = 0.0013m

Tan Theta = 0.0013 = y/x = y/2.17

red y= 0.00283

yellow-green:

Sin theta = 3 (5.65 x 10^-7) / (1.53 x 10^-3) = 0.0011

Tan theta = 0.0011 = y/x = y/2.17

yellow-green y= 0.0024

red y - yellowgreen y = .00283 - .0024 = 0.00043

Sin Theta = 3(6.65 x 10^-7) / (1.53 x 10^-3) = 0.0013m

Tan Theta = 0.0013 = y/x = y/2.17

red y= 0.00283

yellow-green:

Sin theta = 3 (5.65 x 10^-7) / (1.53 x 10^-3) = 0.0011

Tan theta = 0.0011 = y/x = y/2.17

yellow-green y= 0.0024

red y - yellowgreen y = .00283 - .0024 = 0.00043

This is not right for some reason.

What am I doing wrong?