Electromagnetic Spectrum Discovering Invisible Light LAB adapted from GEMS Becky Hedstrom  Feb 2012

Light Sources What are some other sources of light energy that we can see?

Light Sources How can we define something as a SOURCE of light??

Sources *must generate and emit (give off) the light them selves. * glow and give off their own light. Example: Stars, including our Sun, are sources of light

Light Sources While most objects reflect (or bounce back ) light to some degree. They are NOT considered to be the source of that light themselves. Example: The moon reflects the light of the sun- that’s how how we are able to see it. But the moon is NOT a source of light itself

Light DETECTORS Where are some light detectors in this room? Are there any others light detectors that you can think of? How about the ones located a few centimeters below your eyebrows? : )

Light Transmitters Some materials allow visible light through are called transmitters. There are 3 qualities of transmitters: TRANSPARENT - allows visible light to transmit, or pass through, clear enough to be seen through TRANSLUCENT - admitting and diffusing light so that objects cannot be seen clearly; only partly distinguished OPAQUE - NOT transmitting or allowing light to pass through.

Light SHIELDS How can we define something as a SHIELD of light? Any materials that do not let light waves or particles pass through Example: Aluminum foil would be a “ SHIELD that works ” for visible light - like this flashlight.

Light TRANSMITTERS What are some other things that DON’T shield light, - instead allowing the transmission of visible light? transmit = let light waves or particles pass through) Examples: clear glass, clear plastic, water, oil

Light Transmitters Some materials allow visible light through are called transmitters. There are 3 qualities of transmitters: TRANSPARENT - allows visible light to transmit, or pass through, clear enough to be seen through TRANSLUCENT - admitting and diffusing light so that objects cannot be seen clearly; only partly distinguished OPAQUE - NOT transmitting or allowing light to pass through.

Besides visible energy we see in this room- INVISIBLE energy is all around us!

Stations #1 - #6 each with 1. a SOURCE of energy, 2. a DETECTOR of that energy, and 3. a set of different materials to test/identify as energy TRANSMITTERS or SHIELDS to see which materials may be able to block the invisible energy

STATION 1 VISIBLE LIGHT  SOURCE  (flashlight) STATION 1 VISIBLE LIGHT  DETECTOR  (white paper) is being called the detector because it reflects the light and thus allows our EYES to see it  So our EYES are really DETECTORS : )

INVISIBLE LIGHT WORKSHEET record Predictions and Observations TEST SHIELD FLASH LIGHT STATION 1 Visible Light BLACK LIGHT STATION 2 Ultra violet Clear plastic Pred / T / / T Result Pred, / / Result Black Plastic Pred. / S / / Result Pred, / / Result Arrival at new station: MARK PREDICTIONS * on Left side of Station Row 7-10 min. at each station * KEY S = Shield T = Transmitter HANDLE all items GENTLY! Try folding materials into several layers VOICES: LOW VOLUME Auditory Cue signals ROTATION to Next higher # ( #7 go to #1)

Get ready for some surprises!  At Station #1 VISIBLE LIGHT,  making predictions about  which materials transmit light,  and those which block light is fairly easy –  but not so much,  with invisible energies!  Travel with Lab sheets and pencils as groups and have fun exploring!

De-Briefing Station # 1 VISIBLE LIGHT  SOURCE = flashlight  DETECTOR = white paper (used to reflect or bounce back the visible light so our eyes can identify it  DETECTORS Our EYES

De-briefing Station # 2 INFRARED Energy  SOURCE = HEAT LAMP (infrared bulb)  DETECTOR = Students’ hands  (optional- Digital camera or video  camera)

De-briefing Station # 3 Remote Control  SOURCE = Remote control  DETECTOR = TV or overhead projector or other device triggered by remote

De-Briefing Station # 4 RADIO STATION (set to set to receive FM stations) SOURCE = RADIO STATION  DETECTOR = radio itself is a detector of  radio waves received at  FM frequencies- called  Megahertz (MHZ or 10 6 )  10 6 refers to cycles  (peak to peak)  per second

RESULTS Station #5 RADIO (set to set to receive AM stations)  SOURCE = Radio station  DETECTOR = DETECTOR = radio itself is a detector of  radio waves received at  AM frequencies- called  Kilohertz (KHZ or 10 3 )  10 3 refers to cycles  (peak to peak)  per second

DeBriefing RADIO Reception, cont’d. While batteries are powered by energy source of batteries or electricity, producing sound energy our focus today is discovering the source /location – where are the signals coming from that convert to radio waves to provide the sound energy we can hear? Yes- the source is a radio transmission tower - located at a distance. The information to produce sounds we hear on the radio is encoded in the waves transmitted from the radio tower. The radio is the detector of radio waves.

De-Briefing Station # 7 X-RAY Energy and #8 GAMMA RAY Energy # 7 #8 X RAY GAMMA RAY  SOURCE = x ray machine generated by cosmic objects Sun gives off x-rays during and radoiactive atoms, also  solar flares in nuclear explosions  DETECTOR = Geiger counter

SUMMARIZING LIGHT Energy can be both VISIBLE and INVISIBLE: 1. Name of invisible light used in remote control device? 2. What kind of invisible energy do we cook with? 3. What kind of waves are received by satellite TV dish? 4. On a trip to dentist, lead shield aprons protect from radiation of vital organs from what type of energy? 5. What kind of energy is invisible to humans, but can be seen by some animals?

SUMMARIZING (KEY) LIGHT Energy can be VISIBLE and INVISIBLE: 1. Name of invisible light used in remote control device? infrared 2. What kind of invisible energy do we cook with? microwave 3. What kind of waves are received by satellite TV dish? microwaves 4. On a trip to dentist, lead shield aprons protect from radiation of vital organs from what type of energy? X-ray 5. What kind of energy is invisible to humans, but can be seen by some animals? infrared

Electromagnetic Spectrum Discovering Invisible Light LAB adapted from GEMS Becky Hedstrom  Feb 2012