Focusing on Light What is light? Is it a particle or a wave? An age-old debate that has persisted among scientists is related to the question, "Is

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2 Focusing on Light What is light? Is it a particle or a wave? An age-old debate that has persisted among scientists is related to the question, "Is light a wave or a stream of particles?" Very noteworthy and distinguished physicists have taken up each side of the argument, providing a wealth of evidence for each side. The fact is that light exhibits behaviors that are characteristic of both waves and particles. Light is a form of energy and travels in the form of electromagnetic waves

3 Why is the sky blue? Light and Color The light from the sun looks white. But it is really made up of all the colors.

4 Light and Color All light travels in a straight line unless something gets in the way and does one of these things: reflect it (like a mirror) bend it (like a prism) or scatter it (like molecules of the gases in the atmosphere)

5 Light and Color Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.

6 At Sunset: As the sun gets lower in the sky, its light is passing through more of the atmosphere to reach you. Even more of the blue light is scattered, allowing the reds and yellows to pass straight through to your eyes.

7 The orange color?? The sky appears orange or red because larger particles of dust, pollution, and water vapor in the atmosphere reflect and scatter more of the reds and yellows.

8 Let s look at the movement of energy, or waves.

9 WHAT ARE WAVES?

10 Waves: Waves are vibrations that transfer energy from place to place without matter moving Waves can be described by their amplitude, wavelength, frequency, and speed Some waves have to travel through a medium (solid, liquid, or gas) Electromagnetic waves can travel through empty space

11 Important to understand!! Waves transmit energy: Waves do not move matter from one place to another Instead, energy moves from places to place through waves If matter moves, it vibrates up and down or side to side But the matter then returns to its original position

12 Types of Waves Fill in the missing information on your page.

13 Mechanical Waves These waves are classified by how they travel through a medium (solid, liquid or gas) Three classifications: Transverse Longitudinal Surface

14 Longitudinal Waves In longitudinal waves, the particles of the medium are moved parallel to the direction that the waves are traveling

15 Longitudinal Waves - Demo Draw in your box the image below: Demo can we replicate the box?

16 Transverse Waves Transverse waves in which particles of the medium move in a direction perpendicular to the direction that the wave moves.

17 Surface Waves Combinations of transverse and longitudinal waves. Surface waves can only move along the surface of the planet like ripples on water.

18 Wave Movement Animation

19 Watch the movement - Animation:

20 Parts of Waves

21 Amplitude The amplitude of a wave is its maximum disturbance from its undisturbed position. Draw the amplitude on your page

22 What are the amplitudes here?

23 Wavelength The wavelength of a wave is the distance between a point on one wave and the same point on the next wave Crest the highest part of a wave Trough the lowest part of a wave

24 Frequency (of a wave) Frequency - The frequency of a wave refers to how often the particles of the medium vibrate when a wave passes through the medium. The unit is often in Hertz (Hz). 1 Hz is equivalent to 1 cycle/second How it works: If a coil of slinky makes 3 vibrational cycles in one second, then the frequency is 3 Hz. And if a coil makes 8 vibrational cycles in 4 seconds, then the frequency is 2 Hz (8 cycles/4 s = 2 cycles/s).

25 Frequency

26 Speed of waves: Different types of waves travel at different speeds The speed of a wave can be calculated from its frequency and wavelength Speed =Wavelength x Frequency

27 Light and Energy

28 EM Spectrum A second way that waves are characterized is by the types of matter they travel through. Electromagnetic waves, including light waves, do not require a medium to carry energy This is how we get radiant energy from the Sun - no matter is required for that energy to reach Earth Scientists can gather information about the universe from these different types of waves

29 Electromagnetic Waves Light is a form of energy that travels in the form of electromagnetic waves Electromagnetic waves are transverse waves that have electrical and magnetic properties EM Waves travel in a straight line known as a Ray

30 Electromagnetic Waves Can travel through both empty space and matter

31 Light and Energy

32 Electromagnetic Wavelength All electromagnetic waves travel at the same speed, but they have different wavelengths and different frequencies

33 Use this page for the next section colored pencils would be great to circle the waves Be sure to make a key for the colors! My key: Blue -radio Green micro Red infrared Visible - orange UV - purple X-ray grey Gamma - yellow

34 Electromagnetic Spectrum The electromagnetic spectrum is the range of electromagnetic waves in order of increasing frequency (write frequency at the top of your page, then write wavelength at the bottom) Microwaves

35 Circle pick a color Radio Waves Radio waves are the electromagnetic waves with the longest wavelengths and the lowest frequencies (which box do we put it in?) Uses: Your radio captures radio waves emitted by radio stations, bringing your favorite tunes. Radio waves are also emitted by stars and gases in space.

36 Microwaves Microwaves are radio waves with the shortest wavelengths and the highest frequencies Uses: Microwave radiation will cook your popcorn in just a few minutes, but is also used by astronomers to learn about the structure and distances of nearby galaxies.

Infrared Rays Infrared light lies between the visible and microwave portions of the electromagnetic spectrum Far infrared waves are thermal Uses: Night vision goggles

37 Infrared Rays Infrared light lies between the visible and microwave portions of the electromagnetic spectrum Far infrared waves are thermal Uses: Night vision goggles pick up the infrared light emitted by our skin and objects with heat. In space, infrared light helps us map the map cooler objects, such as planets, cool stars, and nebulae

Visible Light The part of the spectrum that you can see Each different wavelength of light has a different color The longest wavelength is red, the shortest wavelength is violet Most visible light

38 Visible Light The part of the spectrum that you can see Each different wavelength of light has a different color The longest wavelength is red, the shortest wavelength is violet Most visible light is a mixture of colors Uses: Our eyes detect visible light. Fireflies, light bulbs, and stars all emit visible light. Space Uses: The relationship between color and temperature is used to study stars

Ultraviolet Rays Ultraviolet (UV) light has shorter wavelengths than visible light These waves are invisible to the human eye, but some insects, like bumblebees, can see them.

39 Ultraviolet Rays Ultraviolet (UV) light has shorter wavelengths than visible light These waves are invisible to the human eye, but some insects, like bumblebees, can see them. Uses: Ultraviolet radiation is emitted by the Sun and are the reason skin tans and burns. "Hot" objects in space emit UV radiation as well. UV light is used to study the structure and evolution of galaxies!

X-Rays X Rays have very short wavelengths and high energy Uses: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag.

40 X-Rays X Rays have very short wavelengths and high energy Uses: A dentist uses X-rays to image your teeth, and airport security uses them to see through your bag. X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection. X-ray emission is expected from objects that contain extremely hot gasses at temperatures from about a million kelvin (K) to hundreds of millions of kelvin

41 Gamma Rays Gamma rays have the shortest wavelengths and highest frequencies Everyday Uses: Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells Space Uses: Since high-energy processes tend to produce high-energy radiation, gamma rays are emitted by some of the most exotic structures in our universe: exploding stars (supernovae), neutron stars, black holes, and quasars.

42 Your page should be complete! Be ready to write down the number of the next slide, it would be good to print in color at home or put into a doc!

44 LAB EM WAVES A look at the relationship between wavelength and frequency

Electromagnetic radiation simply a stream of photons (a bundle of energy) What are photons???

Electromagnetic radiation simply a stream of photons (a bundle of energy) What are photons??? no mass travel in a wave like pattern move at the speed of light contain a certain amount (or bundle) of energy