[Hint: the path difference δ and phase difference φ are obviously related by δ/λ = φ/(2π).] A screen is illuminated by monochromatic light whose wave length is λ, as shown. The distance from the slits to the screen is L.

At the third bright fringe on the screen (position y on the screen), δ (the corresponding path length difference) and φ (the phase angle difference) is given by

1. δ = 7/2 λ and φ = 7 π

2. δ = 13/2 λ and φ = 13 π

3. δ = 9/2 λ and φ = 9 π

4. δ = 3/2 λ and φ = 3 π

6. δ = 11/2 λ and φ = 11 π

7. δ = 2 λ and φ = 4 π

8. δ = 5 λ and φ = 10 π

9. δ = 3 λ and φ = 6 π

10. δ = 6 λ and φ = 12 π