Experimental question: how does a change in medium effect light? : i need a hypothesis: answer for 34pts

The cerebellum controls? thirst sensations sleep-wake cycles hand-eye coordination heart rate and pulse

Light from a sodium lamp passes through a diffraction grating that has 1000 slits per millimeter. the interference pattern is viewed on a screen 1.000 m behind the grating. the first (m = 1) two bright yellow fringes that are visible are 0.7288 m and 0.7300 m from the central maximum. what are the wavelengths of these two fringes?

What does si stand for,when referring to a system of measurement