The amount of movement of the particles depends on the amount of acting on them and their relationship to other atoms.

The amount of movement of the particles depends on the amount of Force acting on them and their relationship to other atoms.

Explanation: The amount of movement of the particle depends on the amount of force acting on them and their relationship with other atoms i.e. the inter-atomic force acting. If the inter-atomic distance is small, more force would act and there would be less movement of the particles. For example in solids. As the inter-atomic force reduces, the inter-atomic distance increases, the amount of movement increases. For example in liquids and gases.

wavelength divides in half and speed stays the same.