Answer:
1. Independent
2. Dependent
3. width of barrier line
Step-by-step explanation:
1. The independent variable is the one that does not depend on any variable and it can be set to any value. Thus, wavelength is Independent variable.
2. The dependent variable is the one which depends upon the value of other variables, like diffraction angle here depends upon the wavelength. Thus, diffraction angle is Dependent variable.
3. The parameter kept constant of the barrier is the width of barrier line. Multiple lines are drawn on diffraction grating to provide obstruction to wave. Their width is always kept constant.