# Wave aspect of light( index of refraction)

1. Jun 4, 2013

### saba sha

hello
if the fish is swiming below the water, and we need to catch it, we will spear the fish above, below or at the fish? if we will use laser light, thn above, below or at the fish?

2. Jun 4, 2013

### tiny-tim

hi saba sha!

tell us what you think, and then we'll comment!

3. Jun 5, 2013

### saba sha

if i know the answer to this question, why i posted it here.......:(
laser light mere guess above the fish.

4. Jun 5, 2013

### tiny-tim

no need to guess, you can work it out! :tongue2:

first, draw a diagram showing the surface of the water (that'll be a horizontal line), the fish (under the water), a nice big eye (above the water), and a second (bent) line that light follows from the fish to the eye (which enables the eye to see the fish in the first place)

mark the angles of incidence and of refraction, and write the formula for them​

then do the same thing all over again, in a second diagram, but this time with a line that the laser light follows from the eye to the fish instead of the original second line

what do you notice?

(btw, laser light behaves like ordinary light, you can forget that it's from a laser)

(and assume the fish is so slow that you can assume it's stationary)

5. Jun 5, 2013

### saba sha

thats right but the formula is to find the angle of incidence with the surface. not about the depth of the surface

2nd question is about. as light waves stretched or squeezed with the speed they enter the surface. do this matter as well?

6. Jun 5, 2013

### tiny-tim

yes, but if the angle is bigger, then the light goes deeper, so the angles do help you to find the depth

draw the two diagrams …

what do you notice?​

sorry, i don't understand you

7. Jun 6, 2013

### saba sha

as light move from 1 medium to another medium it stretched or squezed depending on the speed. please clear it.
still i am unable to understand even after fig with which angle and where should i spot the lite?

8. Jun 6, 2013

### tiny-tim

can you show us your two diagrams?

(or describe them, particularly describing any difference between the two diagrams)

9. Jun 6, 2013

### Drakkith

Staff Emeritus
When the light enters a medium with a different index of refraction the wavelength changes. (But not the frequency) if it moves into a higher refractive index the wavelength shortens, since the frequency is the same but the wave's velocity is slower. The opposite occurs when going from a higher to a lower refractive index.

Could you be more specific with where you are having trouble in your problem? Have you done everything suggested to you already? If not, what could you not do?

10. Jun 7, 2013

### saba sha

i am facing problem about where my light will spot and at how much depth it will goes? angle of incidence and refraction i calculated. but depth of light i cant calculate

11. Jun 7, 2013

### tiny-tim

good

show us your calculations (for each of the two diagrams)​

12. Jun 7, 2013

### saba sha

how i show you?

13. Jun 7, 2013

### tiny-tim

?? you said …
ok, you calculated, so type out what you calculated!

14. Jun 8, 2013

### saba sha

hmmmmm
as by snells law, angle of incidence and angle of refraction we can calculate.
now the problem i faced is, are we aming perpendicular or at angle? and how we come to know that our our light will hit rightly on target?
how i rite calculations here? new plz guide

15. Jun 8, 2013

### tiny-tim

at an angle

draw the fish on the left and the eye on the right, and a (bent) line joining them shwoing the path of the light

16. Jun 8, 2013

### saba sha

that drawn......light moved and and refracted as entered into water......now above fish or below fish?