# Light Waves Interference

1. Aug 16, 2010

### roam

1. The problem statement, all variables and given/known data

A laser beam ( λ = 694 nm) is incident on two slits 0.100 mm apart. Approximately how far apart (in m) will the bright interference fringes be on the screen 5.00 m from the double slits?

2. Relevant equations

$$y=L\left( \frac{m \lambda}{d} \right)$$

3. The attempt at a solution

$$y_{m+1}-y_m = L \left(\frac{(m+1)\lambda}{d} \right) - L \left( \frac{m \lambda}{d}\right)$$

$$= L\frac{\lambda}{d}= 5 \left( \frac{694}{1 \times 10^{-4} m} \right)$$

=34700000

So I got the distance between adjacent fringes to be 34700000 which is a very huge number. But the right answer must be 3.47 × 10–2. Any help is appreciated.

2. Aug 16, 2010

### Staff: Mentor

For one thing, the wavelength is 694 nm, not 694 m. (nm = nanometer)