# Electromagnetic Waves Class 12 Notes Physics Chapter 8

#### Chapter at a Glance

1. An EM-wave consists of oscillating electric and magnetic fields. An EMĀ­ wave travelling along an x-axis has an electric field E and a magnetic field iJ
with magnitudes which depend on x and t :

2. The e.m f. waves do not require a material medium for their propagation and form a set of orthogonal vectors.

3. The electric field vector E and the magnetic field vector B vary sinusoidally, always in the same phase. They attain their peak values E0, B0 at the same place at the same time.

4. Maxwell discovered that all the basic principles of electromagnetism can be formulated in terms of four fundamental equations, called Maxwell’s equations. These are:

5. The rate per unit area at which energy is transported via an electromagnetic wave is given by the Pointing vector

6. The time-averaged rate per unit area at which energy is transported, is called the intensity of wave:

7. Energy associated with an electromagnetic wave is

8. The electromagnetic spectrum is the orderly arrangement of EM wave, the range of spectrum varies from 10-12m to 104m i.e., from y-rays to radio waves.

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