Interference A laser emitting light of wavelength 550 nm is used to illuminate two parallel slits, giving two coherent sources. Interference fringes are produced on a screen 3.0 m from the slits. The separation of the fringes is 3.3 mm. a) Calculate the distance between the centres of the two slits. b) State how the separation of the fringes changes if light of a shorter wavelength were used. c) With reference to the term path difference, explain why the bright fringes are observed on the screen.

Interference A laser emitting light of wavelength 550 nm is used to illuminate two parallel slits, giving two coherent sources. Interference fringes are produced on a screen 3.0 m from the slits. The separation of the fringes is 3.3 mm. a) Calculate the distance between the centres of the two slits. b) State how the separation of the fringes changes if light of a shorter wavelength were used. c) With reference to the term path difference, explain why the bright fringes are observed on the screen.