Lens and Mirror immersed in water

[qw098]

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Hi, I found this question in my TBR book.

When a lens and a mirror are immersed in water, we find that the focal length of the lens:
A) and mirror both increase.
B) decreases, while the mirror remains the same.
C) increases, while the mirror remains the same.
D) and mirror both remain the same

The answer is C (<---Highlight to see answer)

In the answer it says: "If a lens is immersed in water, then the medium surrounding the lens has a higher index of refraction, which results in less bending of the light rays. By bending less, the rays intersect farther from the lens, meaning that the focal length increases."

I guess my question comes down to: Wouldn't the medium surround the lens that has a higher index of refracting result in the MORE bending of the light rays?

Thanks!

 

[milski]

The amount of bending depends on the ratio between the refracting indices of the two medias. When they are exactly the same, there is no bending. Since both water and glass having higher refracting index than water, their Rw/Rg will be closer to one than Ra/Rg and the lens will bend less under water.

 

[qw098]

The amount of bending depends on the ratio between the refracting indices of the two medias. When they are exactly the same, there is no bending. Since both water and glass having higher refracting index than water, their Rw/Rg will be closer to one than Ra/Rg and the lens will bend less under water.

A+! Thank you kindly! 🙂

PS: Is there a lot of optics on the real MCAT, it's my weakest part 🙁

 

[milski]

A+! Thank you kindly! 🙂

PS: Is there a lot of optics on the real MCAT, it's my weakest part 🙁

You're welcome! 👍

No idea about the real MCAT - I'm yet to take it.

 

[Temperature101]

A+! Thank you kindly! 🙂

PS: Is there a lot of optics on the real MCAT, it's my weakest part 🙁

I heard it's usually one discrete, but I dont know how true is that.