Geometric Optics question TBR

[deleted783484]

Which of the following statements are true about the index of refraction of a substance?

I- it is inversely proportional to the speed of light in the substance
II- it depends on the properties of the substance
III- it depends on the radius of curvature of the substance
IV- It can have a value less than 1.

A- I and II only
B- I,II,III only
C- II and III only
D- I,II,III,IV

Answer is A. I picked B.

So I understand why I, II are correct and why IV isn't but i don't understand statement III and why it's incorrect at all?

The explanation they gave to why III is incorrect was: although the light may be bent differently with a radius of curvature this has to do with the incident angle and not the index of refraction"

Thanks!

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[aldol16]

Index of refraction is a property that is inherent to a material. It describes how light moves through the material generally and not the specifics of refraction for a specific contour. In other words, glass has a certain index of refraction. It doesn't matter what the shape of that glass is, the index of refraction is a property of the material, i.e. glass, itself. In equation form, index of refraction is n = c/v. You'll notice that "radius of curvature" does not enter into the calculation.

 

[deleted783484]

Index of refraction is a property that is inherent to a material. It describes how light moves through the material generally and not the specifics of refraction for a specific contour. In other words, glass has a certain index of refraction. It doesn't matter what the shape of that glass is, the index of refraction is a property of the material, i.e. glass, itself. In equation form, index of refraction is n = c/v. You'll notice that "radius of curvature" does not enter into the calculation.

Makes sense! Thank you!!

 

[BerkReviewTeach]

This is a very typical trick applied by test writers. They know you use something in a common calculation, so they make that an answer choice. The index of refraction can be calculated from the radius of curvature (which is based on the incident and refracted angles) using Snell's Law, but it does not depend on that value. The fundamental value it depends on is speed of light in a given medium.

Another example of this would be asking whether the atomic radius depends on (a) the electronegativity, (b) the ionization energy, (c) the electron affinity, or (d) the Zeffective for an element. All of the period trends (atomic radius, electronegativity, ionization energy, and electron affinity) depend on the valence shell and the effective nuclear charge. Because they all depend on the same thing, it is easy to errantly think they depend on each other.

 

[deleted783484]

This is a very typical trick applied by test writers. They know you use something in a common calculation, so they make that an answer choice. The index of refraction can be calculated from the radius of curvature (which is based on the incident and refracted angles) using Snell's Law, but it does not depend on that value. The fundamental value it depends on is speed of light in a given medium.

Another example of this would be asking whether the atomic radius depends on (a) the electronegativity, (b) the ionization energy, (c) the electron affinity, or (d) the Zeffective for an element. All of the period trends (atomic radius, electronegativity, ionization energy, and electron affinity) depend on the valence shell and the effective nuclear charge. Because they all depend on the same thing, it is easy to errantly think they depend on each other.

Thank you!!