1. Consider the Following ??

2. What is Light

3. Electric Field...
Is the space around an electric charge, it does not have mass.
It is not matter
It 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 matter
it is detected by the force it exerts on other magnetic materials
Magnetic field also is energy

5. Do electric and magnetic fields interact?
Static (not moving) Electric field does not exert force on magnetic materials
Static (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 magnet
Similarly,
Moving or alternating (changing in strength) magnetic field will generate electric field.

7. Electromagnetic Wave
Electric and magnetic fields may pass energy one to another without any wire
This energy moves ahead (propagates) in a straight line at 300,000 km/s
Electromagnetic wave is a transfer of energy by constant interaction between electric and magnetic fields.

8. Like in Transversal Water Waves,
amplitude
Direction of
propagation
Particles of medium (a toy duck and water itself) do not move ahead, but swinging up and down
Energy 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 forth
Energy moves ahead
(Watch animation of sound wave now)

10. Mechanical Waves vs Electromagnetic Wave
water wave: energy moves ahead by vibrating water
Sound wave: energy moves ahead by vibrating air
Wave in a rope: rope twists to send energy impulse ahead
Electromagnetic 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/s
Short or long, all the waves will make same distance in one second
Shorter waves will get chance to oscillate more times during that time
shorter waves have higher frequency
Shorter waves with higher frequency are more energetic
Frequency(f): # of cycles per second

12. Lower frequencies (long waves)
Wavelength measured in:
km (kilometres)
metres
cm (centimetres)
mm (milimetres)
Continues over!

13. Highest frequencies (short waves)
The other end of spectrum
Wavelength measured in:
nm (nanometres)
1nm = 10-9m
size of protein
or Å (Angstrom)
1 Å = 10-10m
size of water molecule
Even more ouch! - more energy

14. What’s in the Middle of the Electromagnetic Spectrum?
Wavelength measured in:
mm (milimetres), 10-3m
µm (micrometres),10-6m,
Size of bacteria
nm (nanometres), 10-9m
Size of one cell

15. All the wavelength / frequency ranges:
Energy
ROY G BIV

16. Light is an electromagnetic radiation
It is pure energy moving ahead, it does not need medium to propagate
It moves always in the straight lines within same (while in the same) medium
All 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 wave
Which one is more energetic?

19. Light does act as a wave
It can be cut by a narrow slot (polarization)

20. Light does act as a wave
Light diffracts: spreads around when exits narrow gate
When waves overlap, intensities of two waves add up (interferention)