The hydrogen spectrum includes a red line at 656 nm and a blue-violet line at 434 nm. what are the angular separations between these two spectral lines for all visible orders obtained with a diffraction grating that has 4 470 grooves/cm? (in this problem assume that the light is incident normally on the gratings.)

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.