1 What did you do last time? 2 magnify concave refraction convex lens focus PRINT the word next
to the image on the next slide.
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4 Let's take the temperature of the rainbow. You will need: Detecting the Invisible! Do colors have different temperatures? cardboard box prism tape 3-4 thermometers white paper 5 Herschel's Experiment You must have bright sunlight to do this experiment.

Place the paper
at the bottom of the box.
Use the prism to project a rainbow on to the white sheet of paper.
Tape the prism in place.
1 2
6 Place the tip of another thermometer in the indigo blue portion of the rainbow. Record the temperature for each thermometer at the beginning
and in 10 to 15 minutes or when the temperatures stop changing.
Also, record the temperature in the box well outside the rainbow.
Blacken the tip of each thermometer
with a permanent black marker.
Place another in the yellow green part of the rainbow. Place one thermometer just beyond the red part
of the rainbow.
3 4 5
7 Which color had the lowest temperature Which color had the highest temperature Was the area BEYOND the red warmer
or cooler than red
How did this temperature compare with
the temperature on the paper totally outside the rainbow
1 2 3 4 Violet Red Warmer Higher
8 INFRARED The area just beyond the RED
was WARMER than either the cool blue or the warmer red.

The thermometers detected
a form of light that people cannot see!
Click for Video This was one of the great scientific discoveries!
Slide Congratulations! New Layer You have discovered
that there is LIGHT
you cannot see!
Invisible Light
10 Electromagnetic
Wave length in nanometers (nm) Only ONE year after
Herschel's discovery of infrared,
another form of invisible light
was discovered called ULTRAVIOLET.

These invisible forms of light
are part of the
11 There are other invisible forms of light in the You already know most of them! Electromagnetic Spectrum. 12 You cannot see radio waves.

Yet you live in a sea of radio waves.
A radio antenna picks up these invisible waves and
the radio turns them into SOUND.

Radio waves are INVISIBLE --
13 Microwaves You cannot SEE microwaves
but you use microwaves to heat food. Microwaves are invisible
14 Microwave Video 15 You cannot see infrared waves either.

Most warm objects, living or not, emit infrared.

That includes you!

Half the energy radiated by the Sun is in the infrared.
Remote controls use infrared waves
to communicate with other devices.
Infrared waves are INVISIBLE
16 A thermal camera makes the infrared visible.
Here is what a child, a gecko and a scorpion look like in the infrared.
The cold blooded creatures do not radiate much heat.
The warmest objects in the infrared are yellow and white.
Humans are warm blooded. WE MAKE HEAT FROM FOOD.

YOU are not light sources, but you are an INFRARED SOURCE!
Infrared or Thermal Cameras
17 INFRARED What if you had infrared vision? 18 ELECTROMAGNETIC WAVES Visible light is the part
of the electromagnetic spectrum
you can detect with your eyes.
All the colors
of the rainbow!
Visible light
19 Explore the wavelengths
of visible light!
Click Here
20 The German physicist Johann Ritter, having heard of Herschel’s discovery of infrared, looked beyond the violet end of the spectrum and in 1801 discovered ultraviolet light. Ultraviolet ELECTROMAGNETIC WAVE Ultraviolet (UV) light is invisible to humans.
However, many insects ARE able to see UV!

UV light causes both sunburn and tanning.
21 Ultraviolet Seeing the World with a UV Camera 22 Short Video on x-rays X-rays have a much higher energy
than visible light. In fact, x-rays can pass through most objects, including your body.
The calcium in bones and teeth absorb x-rays.
They are opaque to x-rays and can create a shadow.

An x-ray detector creates
an image of these shadows.
X- Rays
23 X-Rays are invisible ELECTROMAGNETIC WAVES. Can Radiation Be Dangerous? The Most Radioactive Places on Earth 24 More on X-Rays - Advanced X-Rays 25 Alpha, Beta and GAMMA! ELECTROMAGNETIC WAVES. Gamma radiation is electromagnetic radiation with the MOST energy and shortest wavelength.

It is produced by nuclear decay, lightning, solar flares, matter-antimatter annihilation, and the interaction between cosmic rays and matter, as well as astronomical sources.

Gamma radiation is used to study the universe, scan containers, sterilize food and equipment, diagnose medical conditions and treat cancers.

Gamma ray are invisible - -
26 More on the Uses of
X-rays and Gamma Rays
27 Electromagnetic Puzzles 28 Electromagnetic Spectrum NASA: Tour of the Electromagnetic Spectrum Light: Visible and Invisible 29