Describe the arrangement, motion, and energy of the molecules in the solid, liquid, and gas phases of water.

This is the number of complete movements of a wave per second.

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?

For two variables in a direct proportion, what is the result of doubling one variable?