Question

can anyone help me out with spectrum its very confusing

Answer 1

see in an electromagnetic spectrum as we move up from violet to red the wavelength increases so frequency decreases u can refer
this fact from plancks quantum theory

Answer 2

The band of colours formed on the screen after the dispersion of light through a prism is called a spectrum. In simple words, when you pass a white light through an equilateral prism, a rainbow like image would be coming out from the other side. This is called spectrum.