TBR index of refraction and bending of light

[4563728]

I've noticed in some of the TBR questions there have been fluctuations in some of the statements they've been making about refractive indexes and bending of light. For example, like number 12, chapter 10 the question asks:

When a lens and a mirror are immersed in water, we find that the focal length of the lens:
a. and mirror increase
b. decreases, while mirror remains the same.
c. increases, while the mirror remains the same
d. and mirror stay the same.

The answer is C and the logic behind the increasing focal length of the lens is, "If lens immersed in water, then the medium surrounding the lens has a higher index of refraction which will result in less bending of light rays..."

But in a earlier question (number 2) that was asking about light passing through a material of various critical angles, it asked which of the four materials would generate the focal point closest to the lens.
The answer was the material that had the smallest critical angle and the explanation for the answer said, "The difference in focal points between the focal points between the four lenses depends strictly on the materials. The material with the greatest index of refraction will bend the light the most and in doing so create a focal point closer to the lens." This seems a bit contradictory to the first question, right?

Also, in an earlier passage discussing a prism (passage 2 in the '25 question' part of the chapter) the passage states, "As the refractive index increases, the degree of refracting increases."

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[4563728]

Any ideas?

 

[4563728]

Bump.

 

[IlyaR]

I ran into that as well when doing TBR.

For all intents and purposes: For a LENS: the focal point is dependent on radius of curvature only when the medium surrounding it has an N equal or very close to 1, ie. vacuum or air. If the medium is something else, the focal length is increased (if I recall, it is multiplied by the n of the medium surrounding the lens, don't quote me on this).

This makes the lens weaker, thus it bends light less. In contrast, a lens with a very small focal length is powerful (1/r) and bends light a lot.

 

[IlyaR]

Also, any mirror's focal point depends ONLY on its radius of curvature, regardless of surrounding medium

 

[Blueprint MCAT Tutor]

This makes the lens weaker, thus it bends light less.

That certainly sounds right to me.

The material with the greatest index of refraction will bend the light the most and in doing so create a focal point closer to the lens.

I'm not looking at the question, so I can't respond to the specific concern about that problem, but that sentence sounds good. You'd just need to add the caveat "The materials with the greatest index of refraction relative to the medium the light is coming from will bend the light the most and create a focal point closer to the lens."

 

[4563728]

This is great. Thanks!!