Final answer:
In the context of a double slit experiment in Physics, if the observed interference fringes spread farther apart with a change in wavelength, the new wavelength must be larger than the original one.
Step-by-step explanation:
The question provided deals with the concept of interference and diffraction in waves, specifically regarding a double slit experiment in Physics. When the wavelength of light (λ) is changed and the interference fringes spread farther apart, it implies that the new wavelength (λ') is larger (longer) than the original (λ).
This relationship is based on the double slit interference formula, which suggests that the distance between bright fringes on a screen (Ay) is directly proportional to the wavelength (λ) given by Ay = xλ/d, where x is the distance from the slits to the screen and d is the distance between the slits. In the double slit experiment, the fringes spread out more when the wavelength is larger, and they spread out less when the wavelength is shorter.