8 labs

My_Files folder/PHSC 1011online/Chapter 7/Home Challenge Lab 7 Optical Challenge.htm

The Optical Challenge

Have you ever been momentarily blinded by the flash of a camera? How long does the sensation last? While the answer will depend on the source and intensity of the light, it is not uncommon for a spot of light to remain for several seconds after the flash occurs. This is due to a phenomenon called “persistence of vision.” When light enters the retina, cis-retinal is quickly converted to trans-retinal. But it takes much longer for trans-retinal to convert back to cis-retinal.

While light can be emitted from various sources either as a continuous flow or as a very rapid series of flashes, our eyes often do not perceive the difference. Why? Because of persistence of vision. Which common light sources do you think are constant light sources? Which ones do you think are flashing light sources? Try this activity and find out.

Materials

•     small, hand-held mirror

•     lamp with incandescent light bulb

•     television

•     other light sources, such as car headlights, streetlights, flashlights, LEDs, and light sticks

Exploration

Step 1   Darken the room and turn on the lamp with the incandescent light bulb. View the light bulb’s reflection in the mirror. Do not stand too close to the lamp; the image should be small. Now, quickly tilt the mirror back and forth. This moves the image across different regions of your retina. Is the image continuous or discontinuous? Do you think the incandescent light bulb is a constant or flashing light source?                  

Step 2   Turn on the television and repeat the experiment. View the television’s reflection in the mirror, and then move the mirror quickly back and forth. Is the image continuous or discontinuous? Do you think the television is a constant or flashing light source?

Step 3   Try this experiment with as many different sources of light as you can find, classifying each as either a constant or flashing light source.

Challenge

How does this experiment and the physiology of your eye allow you to distinguish between constant and flashing light sources?

 

**List at least 2 web pages that discuss the difference between constant and flashing light sources and use the information found on these sites to answer the challenge question in detail.

 

 

 

 

Home Challenge Lab 7  - The Optical Challenge Answer Sheet

 

 

Exploration

 

Step 1:  Incandescent light bulb

 

a.  Is the image continuous or discontinuous?

 

 

 

b.  Do you think the incandescent light bulb is a constant or flashing light source?             

 

 

 

Step 2:  Television

 

a.  Is the image continuous or discontinuous?

 

 

 

b.  Do you think the incandescent light bulb is a constant or flashing light source?

 

 

Challenge

How does this experiment and the physiology of your eye allow you to distinguish between constant and flashing light sources?

 

**List at least 2 web pages that discuss the difference between constant and flashing light sources and use the information found on these sites to answer the challenge question in detail.