What is the wavelength of light that has a frequency of 4.08E14 Hz?

There are weak or strong attractive forces between atoms of liquids with a high viscosity

Crowbar of 5 metre is used to lift an object of 800 metre if the effort arm is 200cm calculate the force applied

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.