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The Electromagnetic Spectrum

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Presentation on theme: "The Electromagnetic Spectrum"— Presentation transcript:

1 The Electromagnetic Spectrum

2 What are Electromagnetic Waves?
Electromagnetic waves are transverse waves produced by the motion of electrically- charged particles.

3 Interesting Thing That Electrically - Charged Do

Aurora Borealis - When electrically charged particles are ejected from the Sun (solar wind) , in a coronal mass ejection, which take two or three days to get here, cause the gas atoms in the sky to glow. It all depends how active the Sun has been. Particles were usually pulled towards the North Pole but if there were enough of them they will travel further down towards the equator . – Keele University UK

5 As the ions approach our atmosphere at the poles it starts interacting with it. The different colors in the aurora are produced by photons (particles of light) that are released in the collisions between the suns wind and our atmosphere. Photons are produced from ionized N atoms regaining an electron, and also when O and N return to a ground (relaxed) state. O atoms involved in collisions produce green or brown-red colors and nitrogen gives off blue as it regains an electron or red as it returns to the ground state.

6 The aurora is a near daily occurrence on Earth
The aurora is a near daily occurrence on Earth. Because the intensity of the light in an aurora is low, it can only be seen at night. The most active and brilliant displays usually occur near midnight. The best time to observe the aurora is between 11 p.m. and 2 a.m. In the northern hemisphere, the best time to view an aurora is during the winter. At latitudes where auroras are common, it is typically light all night in the summer—so you rarely have warm weather and a good aurora. Furthermore, in most polar regions, the weather tends to be clear during the middle of winter—so often the best time to see an aurora is also the coldest.

7 Electromagnetic Waves: Characteristics
The waves radiate from the interacting charged particles, which is why the waves are called electromagnetic radiation.

8 Electromagnetic Waves: Characteristics
Electromagnetic waves consist of electric and magnetic fields at right angles to each other and perpendicular to the direction in which the wave is moving. At point A in the diagram, the field energy is at maximum and starts to decrease, while at point B, the field is at minimum energy and will start to increase.

9 Electromagnetic Waves: Characteristics
Therefore, the electromagnetic wave “leapfrogs” through space, bouncing its energy back and forth between electric and magnetic fields.

10 James Maxwell – Discovered the existence of EM Radiation
In 1864 Maxwell, before the Royal Society of London in 'A Dynamic Theory of the Electro Magnetic Field', said: “We have strong reason to conclude that light itself - including radiant heat and other radiation, if any - is an electromagnetic disturbance in the form of waves propagated through the electro-magnetic field according to electro-magnetic laws.”

11 Electromagnetic Waves: Characteristics
They can travel in the vacuum of space – no need for a medium.

12 Electromagnetic Waves: Characteristics
They can travel at a speed of 300,000 km/s or 186,000 miles/s. (James Maxwell wrote equations that predicted this speed.) When EM waves travel though matter, they are still faster than mechanical waves such as sound. This view of the Cartwheel galaxy was created by combining images captured by four space telescopes: Galaxy Evolution Explorer, Hubble Space Telescope, Spitzer Space Telescope, and Chandra X-ray Observatory.

13 Electromagnetic Waves: Characteristics
Electromagnetic radiation may have particle behavior as well as wavelike behavior. This is referred to as wave-particle duality. (Tiny bundles of light radiation are referred to as photons.) A photon is released as an electron moves back to a lower energy level.

14 Electromagnetic waves are arranged by wavelength in the electromagnetic spectrum.

15 Radio waves have the longest wavelength and the lowest frequency on the electromagnetic spectrum.

16 Types of Radio Waves: AM (amplitude modulation) – the carrier wave is varied or modulated by changing the amplitude. FM (frequency modulation) – the carrier wave is modulated by altering the frequency

17 The radio waves of the highest frequency and energy are called microwaves. Microwaves in microwave ovens cook food by causing water molecules in food to vibrate.

18 Radar waves are a type of microwave energy.

19 Stealth technology can deflect or absorb radar waves

20 Stealth ships

21 Infrared has a wavelength slightly longer than visible light
Infrared has a wavelength slightly longer than visible light. Warm objects give off more infrared radiation than cool objects which can be detected by thermal imaging.




25 Visible Electromagnetic Radiation - Light

26 Visible Light Spectrum of colors

27 Ionizing and nonionizing radiation
Ionizing radiation is radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized. Ionizing radiation can be hazardous to our health.

28 Ultraviolet Radiation - Slightly higher frequency than visible light, it has more energetic photons. It can stimulate skin cells to produce vitamin D, needed for bones and teeth, but over exposure can cause skin damage and possibly skin cancer.




32 X-rays – a shorter wavelength and higher frequency than ultraviolet
X-rays – a shorter wavelength and higher frequency than ultraviolet. It is used in medical diagnosis, as well as airports and quality control in manufacturing.

33 Ways to view a galaxy

34 Gamma Radiation

35 Gamma radiation - highest frequency and most energetic waves of the electromagnetic spectrum. They are emitted from radioactive atomic nuclei. Concentrated gamma rays can kill cancerous cells. It can also kill healthy cells which is why radiation therapy can be difficult for cancer patients.




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