Young-fringe positions scale through a checked path-source wavelength. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Short wavelength lands at two metres
The path source first checks wavelength 1 m. With first order, screen distance six metres, and slit spacing three metres, the fringe position is 2 m.
y=31⋅1⋅6=2
Double wavelength doubles the fringe position
The path source first checks wavelength 2 m. With first order, screen distance six metres, and slit spacing three metres, the fringe position is 4 m.
y=31⋅2⋅6=4
Triple wavelength triples the fringe position
The path source first checks wavelength 3 m. With first order, screen distance six metres, and slit spacing three metres, the fringe position is 6 m.