# Homework Help: What fraction of light is reflected from the air water interface?

1. Mar 2, 2005

### stunner5000pt

What fraction of light is reflected from the air water interface? i.e. How intense is your reflection from a lake?

since the reflection coefficient is $$R = (\frac{n_{2} - n_{1}}{n_{1} + n_{2}})^2$$

n1 = 1 and n2 = 1.33 so R = 0.248. I am not sure how to interprete this?

25% of the light reflects?? is that the appropriate answer?

Last edited: Mar 2, 2005
2. Mar 2, 2005

### learningphysics

Yes. 25% is reflected. 75% is transmitted (refracted).

EDIT: Check your calculation. I get R=0.02, So 2% is reflected.

Last edited: Mar 2, 2005
3. Mar 2, 2005

### stunner5000pt

so th fraction would be 1/4 right? Thanks for the help!!

4. Mar 2, 2005

I get R=0.02

5. Mar 2, 2005

### Jameson

As did I. R = .02

6. Mar 2, 2005

### stunner5000pt

i think you are forgetting to square it it's (0.33/1.33)^2 = 0.062

7. Mar 2, 2005

### Jameson

Nope.

$$(\frac{1.33-1}{1 + 1.33}) = .1416.....$$

$$.1416309^2 = .020059....$$

I don't see the problem.

EDIT: You divided by the wrong number...it's 2.33 not 1.33