Lab 10
Optics Odds and Ends
OBJECTIVES
Explore conceptual odds and ends of optics not covered in lecture.
EQUIPMENT
Optics stuff
Part 1: Microwave Polarization
a. A microwave transmitter emits polarized microwaves and is detected by a
microwave detector. Setup the transmitter, polarizing grating and detector as
shown on the right.
b. Measure the relative intensity as the angle θ of the polarizing grating is rotated
from 0o to 180o.
Optical Polarization
c. Using a light source and an optical polarizer, shine light off of glass and rotate the polarizer
similar to part (b). Is the light reflected from the glass polarizer?
Part 2: The Eye Model
a. Farsighted Eye
A person affected with hyperopia has a shorter-than-normal eye ball, making the retina too
close to the lens system. This causes images of near objects to be formed behind the retina.
 Move the retina screen to the normal slot and find the near point (NP) using a light
source.
 Now move the retina screen to the far slot and describe the image a farsighted person
sees?
 Move the eye model away from the light source. Does a far-sighted person have trouble
seeing distant objects?
 Move the eye model back to the NP and correct the hyperopia by putting eyeglasses on
the model. Find a lens that brings the image into focus when you place it in front of the
eye in slot 1.
b. Nearsighted Eye
A person affected with myopia has a longer-than-normal eye ball, making the retina too far
away to the lens system. This causes images of far-away objects to be formed in front of the
retina.
 Move the retina screen to the normal slot and find the near point (NP) using a light
source.
 Now move the retina screen to the near slot and describe the image a nearsighted
person sees?
 Move the eye model away from the light source. Does a near-sighted person have
trouble seeing distant objects?
 Correct the myopia by putting eyeglasses on the model. Find a lens that brings the
image into focus when you place it in front of the eye in slot 1.
Part 3: Color addition.
We have hung a white screen on the side wall of the lab, and illuminated it with three
overlapping spotlights (R, G and B, of course).
For each of the cases below, predict what you will see, then check your prediction.
Combination of colors
Predicted Color
Observed Color
Red and Blue
___________________________________________________________________
Blue and Green
___________________________________________________________________
Red and Green
___________________________________________________________________
All Three
___________________________________________________________________
Note: We have technical terms for these overlapping colors: “blue-green” = cyan, purplish, or
“red-blue” = magenta, and “yellow” = yellow.
Experiment with making shadows on the wall (with all three lamps together), by putting a pencil
or other object in one or more of the colored light beams. Can you explain the colors you see?
Part 3: Light from warm objects
All objects emit light. As an object gets hotter, it emits more light and it emits light of higher
energy (thus higher frequency and shorter wavelength). Warm objects emit mostly infrared light,
IR, which we can’t see, but this special camera can ‘see’ infrared light!
Use the camera and your eyes to answer the following questions:
 Which emits more IR light – your eyes, or your nose? Why?

Look at a cup of hot water vs a cup of cold water. Which one emits more infrared light?

If we heat something until it gets really hot, do you think it could emit visible light?

Turn on the wire coil and watch it warm up. Does it emit visible light? _____
What color does it emit? _______ Is it still emitting infrared light as well? ______

If we heat up something even more, what will happen to the wavelengths of light it emits?
Use the light bulb filament. Turn up the voltage on the light filament and describe how its
light changes.

While you have the camera in your hand, see if IR light passes through these materials.
Predict first!
Does IR go through?
Prediction:
Test result:
clear acrylic
________
________
glass
________
________
black plastic
________
________
paper
________
________
Part 5: Energy in light
Here we have some fluorescent materials. Light can excite these materials and cause them to
glow, but it has to have enough energy to do so. Try different kinds of light to see if they have
enough energy to excite the fluorescent material.
Does it cause fluorescence?
Light Color
Prediction
Observation
Infrared (warm light bulb)
Red light (red laser)
Green light (laser)
Violet light (laser)
Ultraviolet light (UV lamp – wear goggles)