Equation for object size relative to reflection?

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The discussion focuses on deriving an equation that relates the size of an object, its distance from a small hole, the size of its image on a screen, and the distance from the hole to the screen. Participants suggest using ray optics principles and reference the concept of a pinhole camera. There is a recommendation to accurately represent the small hole in the diagram, emphasizing that it should be much smaller than the object. Additionally, guidance is provided to simplify the ray diagram by removing unnecessary elements. The conversation highlights the importance of precise representation in solving optics problems.
Violagirl
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Homework Statement



The situation below is based upon the image of an object in the presence of a sheet with a small hole and an object that reflects an image onto a screen when shined with a light. The problem is below:

Write an equation that shows the relationship between the length of an object, the distance of the object from a sheet with a small hole, the length of the object's image on a screen, and the distance of the sheet to the screen.


Homework Equations



I'm not sure what equations would be relevant for this situation...

The Attempt at a Solution



See attached document. Any help with determining the equation would be appreciated.
 

Attachments

  • Image of arrow to screen equation.jpg
    Image of arrow to screen equation.jpg
    14.1 KB · Views: 451
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Just draw the situation onto paper. Use ray optics.
This used to be called a pinhole camera or camera obscura. Try it yourself sometime!
Same principle as why people squint to see better ...
 
rude man said:
Just draw the situation onto paper. Use ray optics.
That is what Violagirl has already attempted, in the figure attached to her post.

Violagirl, notice that the problem statement said "a small hole". But the hole in your figure is nearly the size of the object. I would redraw your figure, with the hole very small -- you could just use a small dot to represent the hole.

Then, redraw the rays from the object to the screen.

(Also, those rays you drew to the left of the object are not really needed.)

Hope that helps.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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