Question

If the index of refraction of glass is 1.8 and the speed of light in air is 3.00 · 108 m/s, what is the speed of light in that glass? (Round answer to nearest hundredth.)

1.67 * 10^8
6.00 * 10^-9
5.40 * 10^8

Answer 1

The correct answer is 6.00*10^-9

Step-by-step explanation:

We know the formula n = c/v where n is the refraction, c is the speed of light in a vacuum and v is the speed of light in a medium. Since we know that glass is a medium and not a vacuum, we're looking for v.

n = 1.8

c = 3.00*10^8

v = ?

We can set up our problem like so:

1.8 = 3.00*10^8 (v)

Next, we divide both sides by 3.00*10^8:

1.8/3.00*10^8 = 3.00*10^8 (v)/3.00*10^8

Finally, we get the answer (plug this into your calculator):

6.00*10^-9 = v (on my calculator, the answer shows up as 6E-9 but it's the same number)

Also, I took the test and got that answer wrong on that lesson's quiz. My teacher explained that I messed up the division portion and showed me the correct division which I showed above.

I hope I helped!

Answer 2

Index of refraction of glass (n) = 1.8

Speed of light in air (c) = 3 x 10E8 m/s

Speed of light in glass (v) = ?

We know,

n = c ÷ v
1.8 = 3 x 10E8 ÷ v

Therefore,

v = 3 x 10E8 ÷ 1.8 = 1.666 x 10E8 = 1.67 x 10^8 m/s