05.06 Lens and Mirror Lab

Module 05: Waves and Optics ยท quiz worth 50 pts

The big idea Changing object distance across 2f and f produces a predictable sequence of image locations, sizes, and orientations for a converging lens and a concave mirror.

Treat descriptions as data

This lab records more than distances. The image words are measurements too.

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Variables and evidence

The independent variable is object distance, do. The outcomes are image distance di, real or virtual status, orientation, and relative size. Keep the optical device and its focal length fixed within one data set. Use the assigned simulation's readings; do not substitute this page's sample numbers for your measurements.

Trial method

1. Mark f and 2f

Identify focal length, then mark one and two focal lengths from the device.

2. Place the object

Use the assigned region: beyond 2f, at 2f, between f and 2f, at f, or inside f.

3. Locate the image

Use the displayed rays or screen behavior and record distance with its sign if the tool supplies one.

4. Classify the image

Record real or virtual, upright or inverted, and smaller, same size, or larger.

5. Repeat consistently

Change only dโ‚’ within a device's data set.

Pattern your data should test

Beyond 2f: real, inverted, smaller; image between f and 2f. At 2f: real, inverted, same size; image at 2f. Between f and 2f: real, inverted, larger; image beyond 2f. At f: outgoing rays are parallel, so no finite focused image forms. Inside f: virtual, upright, larger, with negative di. A lens places its real image across the lens; a mirror keeps its real image in front.

Principal-ray diagrams showing how converging lenses and mirrors locate real and virtual images.
Use the ray model to predict the trend your measurements should show before fitting the equation.

Equation check

Lens or mirror equation
1f=1do+1di\frac{1}{f}=\frac{1}{d_o}+\frac{1}{d_i}

Use measured distances in one unit and keep negative dแตข for a virtual image.

Focal length
f=dodido+dif=\frac{d_od_i}{d_o+d_i}

Preserve signs in numerator and denominator.

Magnification
m=โˆ’didom=-\frac{d_i}{d_o}

Compare its sign and magnitude with observed orientation and size.

Worked data check

Real-image trial

  • Object distance. do=30.0โ€‰cmd_o=30.0\,\text{cm}
  • Image distance. di=15.0โ€‰cmd_i=15.0\,\text{cm}

Find f and m.

  1. Calculate focal length.
    f=(30.0)(15.0)30.0+15.0=10.0โ€‰cmf=\frac{(30.0)(15.0)}{30.0+15.0}=10.0\,\text{cm}
  2. Calculate magnification.
    m=โˆ’15.030.0=โˆ’0.500m=-\frac{15.0}{30.0}=-0.500

The observed image should be real, inverted, and half the object's height.

Write the conclusion from your table

Use one measured row from each device with the lens/mirror equation to find both focal lengths, then mark f and 2f beside the matching do values in the tables. Answer the source questions about which do ranges produce real, virtual, and smaller images, what negative di means, and what happens at do = f. In the conclusion, restate the purpose, explain why any valid row gives the same focal length for a fixed device, and cite what your analysis showed. Preserve unexpected measurements and explain them rather than replacing them.

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Lab readiness practice

These questions check procedure and interpretation. Your submitted table still needs your own measurements.

Final checklist

Tick these off as you go. Saved in this browser.