light and optics question TBR

[greenseeking]

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If a normal human eye were focusing on an object 2 meters way, what would be the effective focal length of the eye?

Given, that the typical human eye is spherical in shape, approximately 2 cm long.
answer is 0.02 meters

The back of the book used the 1/f=1/o +1/i formula with o=2 m and i=2cm.

My question is... how do you know what the sign of F is? Is the human eye diverging or converging? should you take into account the sign of F?

 

[MedPR]

If a normal human eye were focusing on an object 2 meters way, what would be the effective focal length of the eye?

Given, that the typical human eye is spherical in shape, approximately 2 cm long.
answer is 0.02 meters

The back of the book used the 1/f=1/o +1/i formula with o=2 m and i=2cm.

My question is... how do you know what the sign of F is? Is the human eye diverging or converging? should you take into account the sign of F?

Human eye is converging. You should be familiar with the basic anatomy of the eye.

Always take into account the sign of f.

 

[milski]

Yep, concave eyes are encountered only in horror movies. 😉

 

[greenseeking]

Yep, concave eyes are encountered only in horror movies. 😉

lol thank you.

 

[MDhopeful74]

bumping an old thread, but why is 2cm the image distance? The passage says "A typical human eye is spherical in shape, approximately 2 cm long. The focusing mechanism of the eye is the cornea-lens system."
What indicates that this is image distance? What am I missing?
This is passage IV from TBR's light & optics practice exam btw.

 

[JustinM88]

bumping an old thread, but why is 2cm the image distance? The passage says "A typical human eye is spherical in shape, approximately 2 cm long. The focusing mechanism of the eye is the cornea-lens system."
What indicates that this is image distance? What am I missing?
This is passage IV from TBR's light & optics practice exam btw.

Our eye's lens needs to form the image at the retina (aka the back of the eyeball). So, the focal length should be 2cm if we want to see things clearly: