Electromagnetic Spectrum

Discovering Invisible Light

LAB adapted from GEMS

Becky Hedstrom Feb 2012

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

Light SourcesHow can we define something as a SOURCE of light??

Sources*must generate and emit (give off) the light themselves.

*glow and give off their own light.

Example: Stars, including our Sun, are sources of light

Light SourcesWhile 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 DETECTORSWhere 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 TransmittersSome 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 distinguishedOPAQUE - NOT transmitting or allowing light to pass through.

Light SHIELDSHow 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 TRANSMITTERSWhat 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 TransmittersSome 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 distinguishedOPAQUE - 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

SHIELDFLASHLIGHTSTATION 1Visible Light

BLACK LIGHTSTATION 2Ultra violet

Clearplastic

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-briefingStation # 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-BriefingStation # 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 106 ) 106 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 ) 103 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