Time it takes for light to travel 54 cm

[crystalspark]

Homework Statement

How do you find the time it takes for light to travel 54 cm through glycerin (index of refraction = 1.470 at 20˚C) in an aquarium?

Homework Equations

These equations might be useful: v= 331 m/s + (0.59 m/s/c˚)(T) niSinθi=nRSinθR

The Attempt at a Solution

v= 331 m/s + (0.59 m/s/c˚)(20˚C)
v= 331 m/s + 11.8 m/s
v= 342.8 m/s

Δt= 0.54 m ÷ 342.8 m/s = 0.0015752 s

But this isn't the right answer

 

[HallsofIvy]

Your problem says "1.470 at 20˚C" which I would interpret to mean that the speed of light in glycerin, at 20˚C, is 1.470 times the speed in vacuum- which would mean that, since you problem asks about the time at 20 C˚, there would be NO correction for temperature.
That is, the speed of light in glycerine, at 20˚C is just the speed of light in vacuum times 1.47.

If I am misinterpreting that, then what is the "0" point for T? 0˚Celcius or (more common) 0˚Kelvin?

 

[crystalspark]

1. Homework Statement

How do you find the time it takes for light to travel 54 cm through glycerin (index of refraction = 1.470 at 20˚C) in an aquarium?

2. Homework Equations

These equations might be useful: v= 331 m/s + (0.59 m/s/c˚)(T) niSinθi=nRSinθR

3. The Attempt at a Solution

v= 331 m/s + (0.59 m/s/c˚)(20˚C)
v= 331 m/s + 11.8 m/s
v= 342.8 m/s

Δt= 0.54 m ÷ 342.8 m/s = 0.0015752 s

But this isn't the right answer

 

[cupid.callin]

is the answer : 2.626 x 10^-9 ?

 

[crystalspark]

is the answer : 2.626 x 10^-9 ?

yes! can you show me how to do it!

 

[cupid.callin]

well i didnt use your first eqn

i used: refractive index = (velocity of light in vacuum = 3 x 10^8) / (velocity of light in vaccum)

find velocity in glycerin and use d=vt

 

[ehild]

[
These equations might be useful: v= 331 m/s + (0.59 m/s/c˚)(T)

That formula might refer to the speed of sound in air.

ehild

 

[berkeman]

is the answer : 2.626 x 10^-9 ?

Please do not give answers to homework questions. That is against the PF Rules (see the link at the top of the page).

 

[berkeman]

1. Homework Statement

How do you find the time it takes for light to travel 54 cm through glycerin (index of refraction = 1.470 at 20˚C) in an aquarium?

2. Homework Equations

These equations might be useful: v= 331 m/s + (0.59 m/s/c˚)(T) niSinθi=nRSinθR

3. The Attempt at a Solution

v= 331 m/s + (0.59 m/s/c˚)(20˚C)
v= 331 m/s + 11.8 m/s
v= 342.8 m/s

Δt= 0.54 m ÷ 342.8 m/s = 0.0015752 s

But this isn't the right answer

Duplicate threads merged. Please take care not to multiple post.

 

[cupid.callin]

OH YES! That eqn is for sound!