Optics B/C

[jkang]

A wave has a phase velocity of 2c (where c = the speed of light in a vacuum). How is this possible?

Not sure, but (Click to Show Hidden Text)

I have two possible explanations: 1. The wave has entered a theoretical material with a refractive index of 0.5. 2. The wave manages to have an incredibly short period.

If neither of those is true then I'm clueless.

Sorry, neither are correct. As a hint, phase is the key word here.

[Adi1008]

A wave has a phase velocity of 2c (where c = the speed of light in a vacuum). How is this possible?

Not sure, but (Click to Show Hidden Text)

I have two possible explanations: 1. The wave has entered a theoretical material with a refractive index of 0.5. 2. The wave manages to have an incredibly short period.

If neither of those is true then I'm clueless.

Sorry, neither are correct. As a hint, phase is the key word here.

I think (Click to Show Hidden Text)

The Theory of Relativity says that information cannot travel faster than the speed of light. The refractive index is a measure of the phase velocity of light, which does not carry information, so it is able to be less than 1.

[jkang]

Not sure, but (Click to Show Hidden Text)

I have two possible explanations: 1. The wave has entered a theoretical material with a refractive index of 0.5. 2. The wave manages to have an incredibly short period.

If neither of those is true then I'm clueless.

Sorry, neither are correct. As a hint, phase is the key word here.

I think (Click to Show Hidden Text)

The Theory of Relativity says that information cannot travel faster than the speed of light. The refractive index is a measure of the phase velocity of light, which does not carry information, so it is able to be less than 1.

This is correct. Because phase velocity doesn't contain information, it has the ability to travel faster than c. The Wikipedia for refractive index has your answer almost word for word. Your turn!

[Adi1008]

Sorry, neither are correct. As a hint, phase is the key word here.

I think (Click to Show Hidden Text)

The Theory of Relativity says that information cannot travel faster than the speed of light. The refractive index is a measure of the phase velocity of light, which does not carry information, so it is able to be less than 1.

This is correct. Because phase velocity doesn't contain information, it has the ability to travel faster than c. The Wikipedia for refractive index has your answer almost word for word. Your turn!

What is the smallest time delay required between two waves of 400nm light to obtain complete destructive interference?

[Tom_MS]

What is the smallest time delay required between two waves of 400nm light to obtain complete destructive interference?

You can answer I just wanted to give it a shot.

I'm getting... (Click to Show Hidden Text)

6.67*10^-16 seconds. This is using the distance over time definition of the speed of light with a 200nm distance to create fully destructive interference.

[Adi1008]

What is the smallest time delay required between two waves of 400nm light to obtain complete destructive interference?

You can answer I just wanted to give it a shot.

I'm getting... (Click to Show Hidden Text)

6.67*10^-16 seconds. This is using the distance over time definition of the speed of light with a 200nm distance to create fully destructive interference.

That's correct; your turn!

[Tom_MS]

That's correct; your turn!

A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.

[Sean_Sylvester1]

That's correct; your turn!

A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.

Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters

[Tom_MS]

That's correct; your turn!

A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.

Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters

Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.

[Sean_Sylvester1]

A certain lens has an index of refraction of 1.5, a front lens radius of 0.09 m, and a back surface lens of -0.04 m according to the cartesian sign convention. If it is 0.10 m thick, determine the front vertex power.

Using the lensmakers formula and its derivation for thick lenses, I came up with an answer of 13.42 diopters

Almost. To find the front vertex power you need to subtract the equivalent focal length by the distance from the front of the lens to the first principal plane.

Is it 64 diopters then? Since the equivalent focal length is the inverse of power and then subtract .09 from that