light and optics

[Temperature101]

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Fiber optic cables can transmit light, because light in the cable achieves total internal reflection as it travels. From which material could the BEST fiber optical cable be made for use in air, if the best cable is one that would let no light rays escape into air, regardless of the degree to which the cable may be bent?

A. An aerogel, with n = 1.05
B. A polymer gel, with n = 1.35
C. Glass, with n = 1.50
D. A plastic, with n = 1.60

Why the answer is D but not A according to Snell's law.

 

[Jepstein30]

Fiber optic cables can transmit light, because light in the cable achieves total internal reflection as it travels. From which material could the BEST fiber optical cable be made for use in air, if the best cable is one that would let no light rays escape into air, regardless of the degree to which the cable may be bent?

A. An aerogel, with n = 1.05
B. A polymer gel, with n = 1.35
C. Glass, with n = 1.50
D. A plastic, with n = 1.60

Why the answer is D but not A according to Snell's law.

So coming from air (n = 1)

Obviously one of the extremes (A or D).

If its 1.05, that's pretty much just air. I'd expect extreme angles necessary to achieve total internal reflection since the two media are essentially equal. I'd go D without doing the calculations.

 

[Temperature101]

So coming from air (n = 1)

Obviously one of the extremes (A or D).

If its 1.05, that's pretty much just air. I'd expect extreme angles necessary to achieve total internal reflection since the two media are essentially equal. I'd go D without doing the calculations.

Intuitively I see that D is the answer but when I use Snell's law I found that the lowest index of refraction will give me the highest critical angle ie greater total internal reflection. Can you do the calculation so I can see what I did wrong?

 

[niblet]

Intuitively I see that D is the answer but when I use Snell's law I found that the lowest index of refraction will give me the highest critical angle ie greater total internal reflection. Can you do the calculation so I can see what I did wrong?

A higher critical angle does not mean greater total internal reflection.

lower index of refraction => higher critical angle => requires a more extreme angle to achieve total internal reflection => less total internal reflection