Question

3. How do you account for the fact that a sharp dividing line does not exist between one type of electromagnetic wave and its neighbor?

Answer 1

A sharp dividing line does not exist as there exist an infinite number of wavelengths between any two values. In contrast to discrete lines, which occur when electrons fall from one bound quantum state to another, a continuous spectrum(which is what the spectrum described in the question is called), occurs when free electrons get bound to an atom and emit a smooth spread of wavelengths. A continuous spectrum emission is described by Planck's Rdiation Law, which states that any body at a temperature above absolute zero emits a continuous spectrum, with intensity peaks at certain wavelengths dependent on the body's temperature.