Please fill in the gaps! i’ll give brainlest:)

Adouble-slit experiment is performed with light of wavelength 600 nm. the bright interference fringes are spaced 1.8 mm apart on the viewing screen.what will the fringe spacing be if the light is changed to a wavelength of 400 nm? ?

What is the acceleration of a spaceship that is initially at rest and then speeds up to 220 m/s in 20 seconds

The boy of mass 30 kg is at r1= 2 meters from the fulcrum. of the girl is 45 kg, at what r2 must she sit so that they are balanced ?