Question

In a double slit experiment with light, bright fringes are observed on the screen. What is the cause of the bright areas?

A. constructive interference because the waves arrive in phase in these areas
B. constructive interference because multiple light sources are arriving at the same spot
C. destructive interference because the waves arrive out of phase in these areas
D. destructive interference because the wave's frequencies cancel each other

Answer 1

Which sort of interference do you think causes bright areas: constructive or destructive?

What is the cause of interference?

Answer 2

Constructive? @broken_symmetry

Answer 3

Yes, constructive is correct

Answer 4

Why though? Why is constructive the answer is what I am not understanding. Which is the correct answer? A or B?

Answer 5

here's a picture of different types of interference in 1D waves that might help

Answer 6

it's to do with the relative phases of the waves

to be in-phase means the waves are "synchronised" and reach their peaks and troughs at the same time so they add

to be out-of-phase means the opposite. one wave reaches a peak when the other is at a trough so they cancel out

Answer 7

Thank you!!