Physics (AS & A Level) · Oct / Nov 2023 · Paper 12 · Question 28

Coherent light of constant wavelength is incident normally on a double slit. Interference fringes are formed on a screen that is a fixed distance from the double slit. The screen is parallel to the double slit. The separation of the slits is varied. Which graph best shows the variation with slit separation a of the spacing x of the interference fringes?

1. AGraph A: x against a, decreasing curve from high x at small a, asymptotic to a-axis
2. BGraph B: x against a, straight line decreasing from positive x-intercept to zero at positive a
3. CGraph C: x against a, straight line through origin with positive gradient
4. DGraph D: x against a, increasing curve through origin, concave up

As printed in the paper