If a sheet containing two very thin slits is heated (without damaging it), what happens to the angular location of the first-order interference minimum? a) It moves toward the centerline. b) It moves away from the centerline. c) It doesn't change. Condition for m-order interference minimum dsinθ=(m+1/2)λ Given this condition, the first order condition its just m=1, thus dsinθ=3λ/2 so, the angular location is, θ = arcsin(3λ/2d) Heating the sheet should cause the sheet expand, this imply the value d (distance between slits) it should be reduced. Therefore, the value of θ it should be increased, which means the answer should be letter b) It moves away from the centerline. However, the student i tried to help told me this is incorrect, the correct answer (he/she's not sure why) is letter a) It moves toward the centerline. But this doesn't make any sense for me, can anyone give me a clue about what am i missing? Thanks in advance.