Objectives:

• To demonstrate the formation of images from convex and concave lenses.
• To identify the type of image formed by convex and concave lenses.
• To confirm the lens equations.

Pre-Lab:

Read and watch the videos in1.5 Refractive Lenses

Procedure: Convex Lens

1. Open thePhET Simulation calledGeometric Optics http://phet.colorado.edu/sims/geometric-optics/geometric-optics_en.html and chooseRun Now!PhET Geometric Optics https://phet.colorado.edu/sims/html/geometric-optics/latest/geometric-optics_en.htmlIf you are unable to run the PhET Simulation here is a https://ophysics.com/l12.html Read the description on the bottom of the webpage for information on how to adjust the distances and lenses.
2. Take some time to play with the simulation to get familiar with how it works. Select Principal rays and change the object to an arrow. Spend some time moving the object and the lens and observing the resulting image.
3. Maximize your screen.Warning: For the measurements taken in this lab, the ruler in the PhET program will not work. Therefore, we will use a standard ruler measuring from the computer monitor.The scale used to make these measurements will change from computer to computer so once you start, you must finish.
4. In this lab, will be moving the object to analyze how images are formed. When you are ready to get started be sure that your settings are as follows:

1. Using the ruler, measure the distance from x to the center line of lens. Record in Data Table 1 as f. Double this value and record as 2f.
2. Measure the height of object (ho) and record.
3. Place the yellow arrow beyond 2f.
4. In Data Table 2, record do, di, hi and your observations of the image.(See image above table 2.)
5. Move the yellow arrow to 2f. Record in Data Table 2 your measurements for do, di, hi and your observations of the image.https://web.pa.msu.edu/courses/2000fall/PHY232/lectures/lenses/images.html Video explaininghttps://www.youtube.com/watch?v=lBKGP6Fh9vs
6. Move the yellow arrow to between 2f and f. Record in Data Table 2 your measurements for do, di, hi and your observations of the image.
7. Place the yellow arrow at f. Record your observations.(Having trouble locating the image? Check your ray diagram sheet, turn on the virtual image, if no measurement can be made record as none.)Record your observations in Table 2.
8. Move the yellow arrow to a position that is halfway between f and the lens. If you can't locate the image, check the box next to Virtual Image. Record your observations in Table 2.

Data:

Table 1 (5 points)
Focal length, f (cm)
2f (cm)
Height of object, ho (cm)

Table 2 (30 points)
Position of Object	Beyond 2f (cm)	At 2f (cm)	Between 2f and f (cm)	At f (cm)	Between f and lens (cm)
do
di
hi
Type of image: real, none, or virtual
Direction of image: inverted or upright

Concave Lens:

1. Go to the following interactive at "The Physics Classroom":https://www.physicsclassroom.com/Physics-Interactives/Refraction-and-Lenses/Optics-Bench/Optics-Bench-Refraction-Interactive

2. Choose the Diverging Lens (Concave)

3. Place your chosen object at 2f. Record f, do, di, hi, and ho into Trial 1 in Data Table 3.(The image may be very small and hard to see - you may want to complete part 4 and come back to part 3)

4. Place your chosen object at f. Record f, do, di, hi, and ho into Trial 2 in Data Table 3.

Table 3 (30 points)
	Trial 1	Trial 2
f (cm)
do (cm)
di (cm)
ho (cm)
hi (cm)
Type of image: real, virtual, none
Direction of image: inverted or upright

Questions and Conclusions:

1. For each of the real images you observed, calculate the focal length of the convex lens, using the lens/mirror equation. Show your work.Note that the equation is for 1/f, so your last step will be taking 1 divided by 1/f to find f. Do values agree with each other? (5 points)

2. Average the values for f found in question 1 and calculate the percent error between this average and the value for f from Data Table 1. (5 points)

What is the value for f from data table 1? This is your theoretical value in the above equation.

3. When does a convex lens act like a magnifying glass?(Where would the object be in relation to the lens and the focal point?) (5 points)

4. Describe the conditions for forming a virtual image with convex and concave lenses.(Where would the object be in relation to the lens and the focal point?) (5 points)

5. How does the image of a concave lens always appear? Where is it located with respect to the lens and the object? (5 points)

6. Research the two basic types of vision problems, farsightedness and nearsightedness, and describe the lens prescription for each. Include diagrams of the eye to show the light paths before and after remediation. (10 points) Here is avideo https://www.youtube.com/watch?v=OydqR_7_DjI