properties of electromagnetic wave
Name: Grade & Section: Score: School: Teacher: Subject: General Physics 2 LAS Writer: JAN JEFFREY R. CAMINA Content Editor: Learning Topic: Properties of an Electromagnetic (EM) Wave; Quarter 4-Week 2 LAS 1 Learning Targets: Relate the properties of EM wave (wavelength, frequency, speed) and properties of vacuum and optical medium (permittivity, permeability, and index of refraction). STEM_GP12OPT-IVb-12 Reference(s): Young, H. and Freedman, R., 2012. University Physics with Modern Physics. 13th ed. 1301 Sansome Street, San Francisco, CA, 94111: Pearson Education, Inc., publishing. pp 1051-1064. Properties of an Electromagnetic (EM) Wave Light is a phenomenon known as an electromagnetic wave. As the name Right-hand rule for an electromagnetic wave: implies, oscillating electric and magnetic fields create electromagnetic waves. In this Point the thumb of your right hand in the section, you will learn more about the nature and the discovery of electromagnetic wave's direction of propagation. waves. 2 Imagine rotating the E-field vector 90 in the sense your fingers curl That is the direction of the B field. Properties of EM waves: 1. The wave is transverse; both E (electric field) and B (magnetic field) are perpendicular to the direction of propagation of the wave. The electric and magnetic fields are also perpendicular to each other. The direction of 90 propagation is the direction of the vector product E x B (Fig. 1). 2. There is a definite ratio between the magnitudes of E and B. E = CB. 3. The wave travels in vacuum with a definite and unchanging speed. 4. Unlike mechanical waves, which need the oscillating particles of a medium such Direction of propagation as water or air to transmit a wave, electromagnetic waves require no medium. = direction of E x B Figure 1. A right-hand rule for The wave speed (v) can be described by the equation below: electromagnetic waves relates the directions of E and B and the direction of propagation. Where: v = VeoErHolly Ver HT n = index of refraction (refer to Attachment A.1 for values at different mediums) c = speed of light (3 x 10 m/s) The frequency (f) the wavelength (A) and the speed of propagation (v) of any periodic wave are related by the usual wavelength-frequency relationship: Electric Field Oscillation v = af Where: -Wavelength- v = wave speed (unit in m/s) A = wavelength (unit in m) f = frequency (unit in Hz) Propagation Example: Magnet Field Oscillation Visiting a jewelry store one evening, you hold a diamond up to the light of a sodium-vapor streetlamp. The heated sodium vapor emits yellow light with a frequency of 5.09 x 1014 Hz. Find the wavelength in vacuum (nvacuum =1) and the wave speed and wavelength in diamond (ndiamond =2.419). Given: Solution: nvacuum = 1 Vvacuum - C (3 x 10# m/s) ndiamond =2.419 Avacuum - = 5.89 x 10 7m nf (1)(5.09 x 10 * Hz) f = 5.09 x 1014 Hz C U diamond = nf 3 x 10 m/s (2.419) -= 1.24 x 10 m/s Avacuum = diamond _ (1.24 x 10 m/S) = 2.44 x 10 'm 5.09 x 1014 Hz Activity: A 90.0-MHz radio wave (in the FM radio band) passes from vacuum into an insulating ferrite (a ferromagnetic material used in computer cables to suppress radio interference). Find the wavelength in vacuum and the wave speed and wavelength in the ferrite (nferrite =3.162). Use the rubrics as your guide in presenting your solution (refer to attachment A.2 at the next page)
