Change the chapter
Question
A tree that is 3 m tall is viewed from a distance of 25 m. If the cornea-to-retina distance of an ideal eye is 2 cm, how tall is the image of the tree on the observer’s retina?
  1. 0.24 cm
  2. 0.5 cm
  3. 0.5 m
  4. 0.08 cm
Question by OpenStax is licensed under CC BY 4.0.
Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 26, Problem 1 (Test Prep for AP® Courses) (0:56)

Sign up to view this solution video!

Rating

No votes have been submitted yet.

Quiz Mode

Why is this button here? Quiz Mode is a chance to try solving the problem first on your own before viewing the solution. One of the following will probably happen:

  1. You get the answer. Congratulations! It feels good! There might still be more to learn, and you might enjoy comparing your problem solving approach to the best practices demonstrated in the solution video.
  2. You don't get the answer. This is OK! In fact it's awesome, despite the difficult feelings you might have about it. When you don't get the answer, your mind is ready for learning. Think about how much you really want the solution! Your mind will gobble it up when it sees it. Attempting the problem is like trying to assemble the pieces of a puzzle. If you don't get the answer, the gaps in the puzzle are questions that are ready and searching to be filled. This is an active process, where your mind is turned on - learning will happen!
If you wish to show the answer immediately without having to click "Reveal Answer", you may . Quiz Mode is disabled by default, but you can check the Enable Quiz Mode checkbox when editing your profile to re-enable it any time you want. College Physics Answers cares a lot about academic integrity. Quiz Mode is encouragement to use the solutions in a way that is most beneficial for your learning.

Calculator Screenshots

OpenStax College Physics, Chapter 26, Problem 1 (AP) calculator screenshot 1
Video Transcript
This is College Physics Answers with Shaun Dychko. The height of the image on the person's retina is going to be divided by the height of the object in real life which is three meters and that ratio is the magnification. It also is the negative of the image distance divided by the object distance. Now, the image distance is the distance between the person's lens of their eye and their retina, which is two centimeters. And, the object distance that we're told is 25 meters. So, we can solve this for Hi by multiplying both sides by Ho. And so, the image height in the retina is going to be the negative of the object height multiplied by the image distance divided by the object distance. So, that's negative three meters times two centimeters written as times ten to the minus two meters divided by 25 meters, which is 0.0024 meters. And, this is 0.24 centimeters. So, the answer is A.