please help with snells law, optics, physics ... - Education Reference

Question by Ida: please help with snells law, optics, physics, science, math!!!!!!!!!!!!?
what is the speed of light in water, n=1.33 knowing the speed of light in a vacuum is 3.0 X 10 to the power of 8 m/s?
a. 2.56 X10 to the eight m/s
b. 2.26 X 10 to the eight m/s
c. 1.38 X 10 to the 8 m/s

i dont get this at all, and i looked in term of my notes and am just really confused, thank you

Best answer:

Answer by blueskies
Speed of light in water = ? Refractive index of water = 1.33 Speed of light in vacuum = 3.0 x 10^8 m/s Refractive index of air= 1.00

Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of velocities in the two media, or equivalent to the opposite ratio of the indices of refraction:

In other words,

sine A_1 ..... v_1 ..... n_2
-------------- = -------- = -------- sine A_2 ..... v_2 ..... n_1

Disregard the sinA_1 : sin3 A_2 ratio on the left side.... and just look at the v's and n's relationship component on the right side....

So you have.....

v_1 ..... n_2
----- = ----------
v_2 ..... n_1

Let's let "1" represent "water".... and "2" represent "air"..... consequently now we have....

v (water) ..... n (air)
------------- = -------------
v (air) ........ n (water)

Now cross-multiply and write the following equation....

-----------------------------------------------------
v (water) x n (water) = v (air) x n (air)
------------------------------------------------------

Divide both sides by " n (water) " , to consequentlylve for " v (water) "..... like this...

v (water ) x n (water) ....... v(air) x n (air)
------------------------------- = ---------------------------
........ n (water) ................. n (water)

The " n (water) " 's cancel out each other on the left side...
........... in that n (water) / n (water) = "1".... and you are left with...

................. v (air) x n (air)
v (water) = ------------------------
................... n (water)

Well, you know v (air) = 3.0 x 10^8 m/s..... right?

You also know n (air) = 1.00, and you also know n (water) = 1.33 .... right?

Okay.... plugging in those merits, you then know what v(water) equals....

................. v (air) x n (air....... 3.0 x 10^8 m/s x 1.00
v (water) = ------------------------ = --------------------------------- = 2.26 x 10^8 m/s
................... n (water) ..................... 1.33

So the answer is B. 2.26 x 10^8 m/s.

That's how you employ Snell's Law to consequentlylve this problem. Hope you find this explanation helpful! =)

What do you contemplate? Answer below!

Source: http://www.qiyic.com/archives/4145

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