Comparison

PP+ Image Formation vs Stars Units Sizes Objects

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

PP+ Image Formation

Features
Read full description

The Image Formation Using Lenses lab uses an optical bench to determine the focal length of a converging lens and to investigate the relationship between the object distance and the image distance. It is part of Polyhedron Physics Plus, a set of 24 iPad apps for use in the classroom. To see how they work, try the FREE PP+ Newton’s 2nd Law lab. For those who’d prefer to develop their own experiments, the PP Optical Bench & Lenses app features a similar apparatus without lab procedures and other supporting materials. In addition to a 3D simulation that produces realistic data, each lab includes introductory videos, background theory, experimental procedure, analysis and reporting tools, pre-lab quiz, post-lab questions, and teacher support materials. The experimental data produced by the simulations are realistic, including random and systematic errors. These features allow students to use standard data analysis and error analysis techniques to report on their own unique data, just as if the experiment had been performed using hands-on equipment. These labs can serve as replacements for hands-on labs, especially when equipment is not available, or as supplements to hands-on labs. They are also a suitable option for students in distance learning and home school situations. Formative and summative evaluations showed no significant difference in learning between students using the virtual labs and those using hands-on labs. Preliminary results suggest increased learning by students using the virtual labs as supplements to hands-on. Polyhedron Physics was developed by Polyhedron Learning Media, Inc. with partial funding provided under contract numbers ED-07-CO-0040 and ED-IES-11-C-0029 from the Institute of Education Sciences in the U.S. Department of Education through the Small Business Innovation Research (SBIR) program.

About

Stars Units Sizes Objects

Explore the vastness of the universe, from the smallest particles to the largest cosmic structures. Compare object sizes, view detailed images, and perform unit conversions across a wide range of astronomical scales. Learn about stars, galaxies, and the incredible distances between them.

Highlights
  • Compare object sizes
  • View object images
  • Pinch/Zoom and Pan images
  • Unit conversion for distances
  • Explore scales from Planck length to observable universe
  • Learn about stars and galaxies
Features
Read full description

Size of the smallest to largest objects and stars. Compare the size of objects in the universe. Object images. Pinch/Zoom image. Pan/Move image. Rotate image. Double tap to reset an image. From the smallest to the largest one. From planck length to observable universe. From Yoctometre, Zeptometre, Attometre, Femtometre, Picometre, Nanometre, Micro, Millimetre, Centimetre, Metre, KiloMetre, Lightyear, Parsecs, Billion Lightyears to 93 Billion Lightyears. Size of objects, particles, atoms, cells, stars and galaxies. Get to know the stars. Get to know the spaces. get to know the universe. How small is this world. How big is the universe. And How great is the creator. How far is the star distance from earth. Two way 18 distance unit conversion. planck length, yoctometer, zeptometer, attometer, femtometer, picometre, nanometre, micrometre, Millimeter, Centimeter, Meter, Kilometer, Inch, Foot, Mile, Astronomical, Lightyear, Parsecs. Perform auto conversion when picker is changed. Share conversion result. Reset unit convertor.

Screenshots

Stars Units Sizes Objects4 screens

Verdict

The call

The clearest difference is price: Stars Units Sizes Objects at Free against PP+ Image Formation's $1.99. Stars Units Sizes Objects also leads on device support (3 vs 1) and iOS requirement (11.0 vs 18.0). PP+ Image Formation's advantage is ads (none vs shown). On update cadence and in-app purchases there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Stars Units Sizes Objects is free to download; PP+ Image Formation costs $1.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

PP+ Image Formation ships an update every 3 months, Stars Units Sizes Objects every 4 months. The most recent releases landed on October 15, 2026 and September 22, 2026 respectively.

Scorecard4 real differences · 6 level
PP+ Image Formation versus Stars Units Sizes Objects: the parameters behind the verdict, then further details
ParameterPP+ Image FormationStars Units Sizes Objects
Price$1.99Free — better
Rating—4.2 (5 ratings) — better
Positive reviews—80.0% of reviews
Number of ratings—5 — better
Update frequencyEvery 3 months — betterEvery 4 months
AdsNo — betterYes
In-app purchasesNoNo
Monetization—Ad-supported
DevicesiPadiPhone, iPad, iPod — better
Requires iOS18.011.0 — better
Further details — not scored
Size91 MB124 MB
Age rating4+4+
DeveloperPolyhedron Learning Media, Inc.Mudarmeen Munlin

In-app purchases

None

PP+ Image Formation

No in-app purchases

None

Stars Units Sizes Objects

No in-app purchases

Questions

Is PP+ Image Formation free?
PP+ Image Formation costs $1.99, with no in-app purchases.
Is Stars Units Sizes Objects free?
Stars Units Sizes Objects is free to download, with no in-app purchases.
Do PP+ Image Formation or Stars Units Sizes Objects have ads?
Stars Units Sizes Objects shows ads; PP+ Image Formation does not.
Which is updated more often, PP+ Image Formation or Stars Units Sizes Objects?
PP+ Image Formation ships an update every 3 months, and Stars Units Sizes Objects every 4 months. Most recently, PP+ Image Formation was updated on October 15, 2026 and Stars Units Sizes Objects on September 22, 2026.

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