Sunlight is used in a double-slit interference experiment. The fourth-order maximum for a wavelength of 470 nm occurs at an angle of θ = 90°. Thus, it is on the verge of being eliminated from the pattern because θ cannot exceed 90° in Eq. 35-14. (a) What least wavelength in the visible range (400 nm to 700 nm) are not present in the third-order maxima? To eliminate all of the visible light in the fourth-order maximum, (b) should the slit separation be increased (show 1) or decreased (show 0) and (c) what least change in separation is needed?