3 Electric Field...Is the space around an electric charge, it does not have mass.It is not matterIt exerts a force on other electrically charged objects and is able to do work.Electric field is …energy
4 Magnetic Field…surrounds magnetic materials, it also does not have mass and also is not matterit is detected by the force it exerts on other magnetic materialsMagnetic field also is energy
5 Do electric and magnetic fields interact? Static (not moving) Electric field does not exert force on magnetic materialsStatic (not moving) Magnetic field does not exert force of electrically charged objects.However….
6 Electric and Magnetic Interaction Moving or alternating (changing in strength) electric field will generate magnetic field. ie an electro magnetSimilarly,Moving or alternating (changing in strength) magnetic field will generate electric field.
7 Electromagnetic WaveElectric and magnetic fields may pass energy one to another without any wireThis energy moves ahead (propagates) in a straight line at 300,000 km/sElectromagnetic wave is a transfer of energy by constant interaction between electric and magnetic fields.
8 Like in Transversal Water Waves, amplitudeDirection ofpropagationParticles of medium (a toy duck and water itself) do not move ahead, but swinging up and downEnergy moves ahead(Watch animation of surface wave now)
9 In Longitudinal Waves (like Sound), Medium (e.g. air) gets more compressed. This repeats again and again. The compression moves away from the source.Particles of medium (air molecules) do not move ahead, they swing back and forthEnergy moves ahead(Watch animation of sound wave now)
10 Mechanical Waves vs Electromagnetic Wave water wave: energy moves ahead by vibrating waterSound wave: energy moves ahead by vibrating airWave in a rope: rope twists to send energy impulse aheadElectromagnetic wave does not need medium. It can travel through vacuum, a space free of matter.Watch animation now
11 Wavelength(λ): max to max distance Speed for all wavelength in vacuum is :V = 300,000 km/sShort or long, all the waves will make same distance in one secondShorter waves will get chance to oscillate more times during that timeshorter waves have higher frequencyShorter waves with higher frequency are more energeticFrequency(f): # of cycles per second
13 Highest frequencies (short waves) The other end of spectrumWavelength measured in:nm (nanometres)1nm = 10-9msize of proteinor Å (Angstrom)1 Å = 10-10msize of water moleculeEven more ouch! - more energy
14 What’s in the Middle of the Electromagnetic Spectrum? Wavelength measured in:mm (milimetres), 10-3mµm (micrometres),10-6m,Size of bacterianm (nanometres), 10-9mSize of one cell
15 All the wavelength / frequency ranges: EnergyROY G BIV
16 Light is an electromagnetic radiation It is pure energy moving ahead, it does not need medium to propagateIt moves always in the straight lines within same (while in the same) mediumAll wavelengths (colours) move at the same speed in vacuum, c = 3.00*108m/s
17 Photons: how light is produced - Electrons within atoms can move from one energy level to another.- Electrons move to higher levels when gain energy; they release energy when move to lower levels.- Light is the energy released by electrons when they change energy level in atoms.- For that, energy has to be input first.
18 Which electromagnetic wave is shorter: gamma ray or radio wave? Which wave is more frequent: gamma ray or radio wave?Gamma waveWhich one is more energetic?
19 Light does act as a waveIt can be cut by a narrow slot (polarization)
20 Light does act as a waveLight diffracts: spreads around when exits narrow gateWhen waves overlap, intensities of two waves add up (interferention)