Optical Bench Lab
Place a lens or mirror on the bench, set the focal length, and slide the object back and forth. The simulator draws the three principal rays and reports the image distance, magnification, and image type. NGSS HS-PS4.
Guided Experiment: Converging lens, real image (d_o > f)
When the object is farther from a converging lens than its focal length, what kind of image forms? How do you expect d_i and m to change as you slide the object closer to the focal point?
Write your hypothesis in the Lab Report panel, then click Next.
Controls
Computed Image
Positive focal length. Element converges parallel rays.
Real image. Rays actually converge on the opposite side, so this image can be projected on a screen. It is inverted because m < 0.
Object height h_o = 4.0 cm·h_i = -2.00 cm·m = -0.500
Data Table
(0 rows)| # | Element | f(cm) | d_o(cm) | d_i(cm) | m | Image Type |
|---|
Reference Guide
Thin-Lens and Mirror Equation
The same equation governs thin lenses and spherical mirrors. Object distance, image distance, and focal length connect through reciprocals.
Solve for d_i to predict where the image forms. Substitute back into the formula to verify your answer.
Magnification
Linear magnification compares image height with object height. The sign tracks orientation. The magnitude tracks size.
Positive m means upright. Negative m means inverted. Values with magnitude greater than 1 mean enlarged. Values between 0 and 1 mean reduced.
Sign Conventions
This lab uses the "real is positive" convention. Each quantity carries its own sign.
- Focal length f is positive for converging lenses and concave mirrors. Negative for diverging lenses and convex mirrors.
- Object distance d_o is always positive (object in front).
- Image distance d_i is positive for a real image and negative for a virtual image.
- Magnification m is positive for upright images and negative for inverted images.
The Three Principal Rays
Any two rays from a point on the object locate the image where they meet (or appear to meet).
- Parallel ray. Travels parallel to the axis, then through (or away from) the focal point on the image side.
- Center ray. Passes through the lens center undeviated, or reflects off the mirror vertex at an equal angle.
- Focal ray. Passes through the near-side focal point, then exits parallel to the axis.
When the rays diverge after the element, extend them backward (dashed lines). Where the extensions meet is the virtual image.
Real-World Optics
Each element type shows up in everyday devices.
- Eyeglasses for nearsightedness use diverging lenses. Glasses for farsightedness use converging lenses.
- Cameras and the human eye place the object well beyond 2f so a reduced real image lands on the sensor or retina.
- Magnifying glasses are converging lenses with the object inside f. The result is a virtual enlarged image.
- Telescopes and microscopes use multiple converging lenses in sequence.
- Concave mirrors focus sunlight and form magnified images in shaving and make-up mirrors.
- Convex mirrors give wide-angle views in security mirrors and vehicle side mirrors.
NGSS HS-PS4 Alignment
This lab supports the NGSS High School Physical Sciences performance expectations on waves and electromagnetic radiation.
- HS-PS4-1. Use mathematical representations to model relationships between wave properties.
- HS-PS4-3. Evaluate claims about wave behavior including reflection, refraction, and image formation.
- HS-PS4-5. Communicate technical information about how electromagnetic radiation is captured by lenses and mirrors in cameras, telescopes, microscopes, and the eye.
Students collect data across many object distances and document the image properties in the lab report panel.
