A World of Light and Color
Activity 2
Beyond the visible?
Procedure and Results Sheet
PART 1
Key Questions:
 Are there types of light other than the colors we can see with our eyes?

How does the intensity of light from an incadescent bulb depend on wavelength?
Materials:
 Computer-interfaced Spectroscope (1)
Below is a schematic of the spectroscope that you will be using in PART 1 of this activity. It
works quite similarly to the hand-held spectroscopes you used in the last activity. Just as in the
hand-held version, the grating, which you can now see, breaks light into its component colors.
angle marker
aperture
1
aperture
2
grating
light detector
light source
movable arm
and platform
This spectrometer is different, though, in that instead of looking at the colors with your eye
(which, by the way, you can actually see the colors shining on aperture 2) we are going to let the
light detector record the brightness of the light that shines on it. The light is emitted by the light
source, passes through aperture 1, split into its constituent colors by the grating, and then passes
through aperture 2 before entering the light detector. The detector informs the computer of the
brightness of the light shining on it while another sensor informs the computer of the angular
position of the movable arm and platform. The computer will use this information to generate a
graph of brightness vs. angle.
1. Rotate the movable arm and platform by holding the arm and rotating it clockwise as seen
from above. Stop moving the arm when it reaches the far edge of the color range on the
violet side. Note the angle of the arm and platform by looking at the angle marker. Write
the angle in the space below.
Violet light begins at this angle: _______o
2.1
2. Continue rotating the arm and platform clockwise until it reaches the far edge of color range
on the red side. Again, note the angle of the arm and platform by looking at the angle
marker. Write the angle in the space below.
Red light ends at this angle: _______o
3. Return the arm and platform to the original position. Be sure arm and platform are at the
0o position.
In a moment, you are going to repeat a procedure similar to above, except you will move the arm
and platform through a much wider angular range. Furthermore, the computer will be recording
brightness at the light detector as a function of angle in much the same way you just did, except
it will do it at many more angular positions and plot relative brightness.
4. Before you make the computer start to graph, make a qualitative sketch on your Prediction
Sheet of what you think the brightness vs. angle graph, generated by the computer, is going
to look like.
STOP
HERE
brightness
5. Click on the button on the screen marked START, which will instruct the computer to begin
graphing.
6. Slowly rotate the arm and platform in a clockwise direction as seen from above until the light
detector is well beyond the angular location of the red in the visible light.
7. Carefully sketch the graph that you see on the monitor in the space below.
angle
Look closely at the graph. Did the light detector begin detecting light affected by the grating at
the angular location of violet? Moreover, did the detector stop detecting light affected by the
grating at the angular location of the red?
8. On your Prediction Sheet, write your answers to the above questions as well as your
explanation for the graph.
9. After the class discusses this point, write an explanation that summaries the group’s
consensus in the space below.
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
2.2
PART 2
Key Questions:
 When visible light travels through one medium then another, what happens to it?
Materials:
 Tinted glass (2)
Pick up one piece of tinted glass and hold it up to a light. You will see the light but it will appear
darker. Now sandwich two pieces of tinted glass together. Looking through the pair, you will
notice that things appear even darker. The question is, “Why?”
1. On your Prediction Sheet list all of the possible reasons you can think of that explain why
objects appear darker when viewed through two pieces of tinted glass.
2. After the class discusses this point, write an explanation that summaries the group’s
consensus in the space below.
3. Hold the two pieces of tinted glass together over a dark surface as shown below.
4. If you were look (don’t do it yet!) at an object reflected off the surfaces of the glasses, do you
think the reflected image will be brighter when reflected from region A or B? Write your
answer on your Prediction Sheet with an explaination.
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
A
B
STOP
HERE
5. Now try it by holding the two pieces over a dark surface. Find the reflection of a fairly bright
object, say a light, and arrange the two pieces of glass so part of the reflection falls in the
region marked A and the rest of the reflection falls in a region marked B. Is the brightness of
the reflected image different in region A than B?
6. Consider again what could explain why objects appear darker when viewed through two
layers of tinted glass. After the class considers and discusses this point, write an explanation
that summaries the group’s consensus in the space below.
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
7. Now discuss with the class the possible paths that light can follow when it encounters glass
and write an explanation that summarizes the group’s consensus in the space below.
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
8.
STOP
HERE
2.3
PART 3
Key Questions:
 Does light beyond red (infrared) act light visible light when it travels from one medium
to the next?
Materials:
 Lamp
 Infrared Radiation Sensor
 Clear glass (2)
You have already seen that the light detector in PART 1 detected light that you couldn’t see. You
can conclude this because you assumed that the invisible light acted just like the visible light – it
was redirected by the grating just as the visible light.
Let’s confirm further that light outside the visible has properties similar to visible light.
The infrared radiation (IR) sensor acts just like the light sensor you used in PART 1, however, it is
portable and is more sensitive to infrared light.
1. Place the infrared radiation sensor so that it points at the light source on your desk. Make
sure the multimeter attached to it is on. What reading do you get on the multimeter when the
light source on your desk is off?
Multimeter reads _________ when light is off.
2. Now turn on the light. What is the reading on the multimeter now?
Multimeter reads _________ when light is on.
3. Assume the multimeter displays a relatively high number when a relatively large amount of
infrared light shines on the IR sensor. In the space below, write what these two results tell
you about the infrared light emitted from the lamp.
STOP
HERE
4. On your Prediction Sheet indicate whether you think the reading on the multimeter will
increase a lot, increase a little, remain the same, decrease a little, or decrease a lot when
you put the clear piece of glass between the source and the probe.
5. Now try it and see what happens.
Multimeter reads _________ when light is on and a piece of glass is between the
light and probe.
6. Can you conclude that infrared light is absorbed by glass?
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
2.4
7. In a moment, you are going to place a second piece of glass between the light and the sensor.
Before you do that, write on your Prediction Sheet what you think is going to happen to the
reading on the multimeter when you put a second piece of glass between the light and the
probe.
8. Try it, and record you multimeter reading below.
Multimeter reads _________ when the light is on and two pieces of glass are
between the light and probe.
9. In the space below, write what the above results informs the class about the absorption
infrared light by clear glass.
10. Now position the IR detector and lamp as shown in the figure below. Then record the reading
from the multimeter in the space below.
TOP VIEW
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
IR Sensor
Multimeter reads _________ when light is on and the probe is pointed as
indicated above.
11. Look at the figure below. On your Prediction Sheet state whether you think the reading
from the IR sensor will change (increase or decrease) from 10, and if so how, when you
arrange the glass, lamp, and sensor as shown below.
TOP VIEW
glass
IR Sensor
2.5
12. Now arrange the glass, light, and probe as indicated, and in the space below enter the reading
from the multimeter.
Multimeter reads _________ when glass, light, and probe arranged as indicated
above.
13. Look at the figure below. On your Prediction Sheet state whether you think the reading
from the IR sensor will change from 12, and if so how, when you place a second piece of
glass in the set-up as shown below.
TOP VIEW
glasses
IR Sensor
14. Now arrange the glasses as indicated, and in the space below enter the reading from the
multimeter.
Multimeter reads _________ when glasses, light, and probe arranged as indicated
above.
15. On your Prediction Sheet, carefully relate how the properties of IR radiation are similar to
visible light within the context of this activity.
16. In the space below, write an explanation that summaries the group’s consensus on how IR
radiation is similar to visible light within the context of this activity.
Kja fkj fdsj j dajf
lfjajf sf ahkjhryo h;
aoe dsfko … Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko Kja fkj fdsj j
dajf lfjajf sf ahkjhryo
h; aoe dsfko Kja fkj
fdsj j dajf lfjajf sf
ahkjhryo h; aoe
dsfko
2.6