What will change the velocity of a periodic wave?

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? ?

How does the image distance (di) of a convex lens compare with the image distance of a concave lens? a. the image distance of the convex lens is positive, and that of the concave lens is negative. b. both are negative for a virtual image. c. both are positive for a virtual image d. the image distance of the convex lens is negative, and that of the concave lens is positive.

The dipole moment of the water molecule (h2o) is 6.17x10^-30 c. m. consider a water molecule located at the origin whose dipole moment p points in the +x-direction. a chlorine ion ( of charge-1.60x10^-19c , is located at x=3.00x10^-9m . assume that is much larger than the separation d between the charges in the dipole, so that the approximate expression for the electric field along the dipole axis can be used. a) find the magnitude of the electric force that the water molecule exerts on the chlorine ion. b) what is the direction of the electric force. -x-direction or +x-direction c) is this force attractive or repulsive?