Physics Homework Help

[Finns14]

In Figure 26.7, suppose that the angle of incidence is 1 = 30.8°, the thickness of the pane is 3.16 mm, and the refractive index of the pane is n2 = 1.33. Find the amount (in mm) by which the emergent ray is displaced relative to the incident ray.

So I think I know how to get the angle it leaves at but I don't know how to get the distance in mm that its shifts. Thanks for the help.

 

[hypn0tik]

Snells Law + simple diagram FTW!

 

[Finns14]

See the thing is I don't exactly know what you mean. i can do the snells law which is , I think, Sin(30.8)*1.33=x then Sin^-1(x) give the angle it leaves at but how do you calculate the rest

 

[hypn0tik]

Originally posted by: Finns14
See the thing is I don't exactly know what you mean. i can do the snells law which is , I think, Sin(30.8)*1.33=x then Sin^-1(x) give the angle it leaves at but how do you calculate the rest

Careful.

I'm assuming you are going from air -> glass -> air.

When you're applying Snell's law as the ray goes from air -> glass, medium 1 is air and medium 2 is glass. So, you have:

sin(30.8) * 1 = 1.33 * sin (r) where r denotes the refracted angle. Solve for r.

Now, the ray travels through the glass at this angle (relative to the normal of course). Using simple geometry (this is where the picture comes in) you can figure out how much the ray has been displaced.

 

[2Xtreme21]

The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

Definitely a "when in doubt, draw it out" problem.

 

[hypn0tik]

Originally posted by: 2Xtreme21
The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

No. Draw a picture.

Edit: Lol. 'Draw it out' is correct.

 

[2Xtreme21]

Originally posted by: hypn0tik

Originally posted by: 2Xtreme21
The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

No. Draw a picture.

The ray is going to travel 3.16mm through the pane because that's how thick it is. He's looking for how far it shifts relative to the normal when it travels through it.

 

[hypn0tik]

Originally posted by: 2Xtreme21

Originally posted by: hypn0tik

Originally posted by: 2Xtreme21
The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

No. Draw a picture.

The ray is going to travel 3.16mm through the pane because that's how thick it is. He's looking for how far it shifts relative to the normal when it travels through it.

Look at what you originally wrote, the part I bolded.

Edit: I know what you're saying, but I'm just being picky about your language, that's all.

 

[Finns14]

Originally posted by: 2Xtreme21

Originally posted by: hypn0tik

Originally posted by: 2Xtreme21
The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

No. Draw a picture.

The ray is going to travel 3.16mm through the pane because that's how thick it is. He's looking for how far it shifts relative to the normal when it travels through it.

Your answer was wrong

 

[2Xtreme21]

Uh, "the ray will travel 3.16mm through the plane"? -_- Either way, it will be one side of a triangle with which you can use the angle to find how much it displaced.

 

[hypn0tik]

Originally posted by: Finns14

Originally posted by: 2Xtreme21

Originally posted by: hypn0tik

Originally posted by: 2Xtreme21
The ray's going to be 3.16mm long, you're going to have the angle. Tan(the angle you get using snell's law) = x / 3.16.

No. Draw a picture.

The ray is going to travel 3.16mm through the pane because that's how thick it is. He's looking for how far it shifts relative to the normal when it travels through it.

Your answer was wrong

How about you show me your attempt before claiming his answer is wrong.

 

[Finns14]

Just red it wrong I apologize let me try it again

 

[Finns14]

I'm sorry I tried the methods you mentioned and they didn't work

 

[Born2bwire]

Originally posted by: Finns14
I'm sorry I tried the methods you mentioned and they didn't work

Not much else to say at this point. You know the angles of a right triangle and you know the length of one of the legs of the triangle. From here it's just geometry.

 

[hypn0tik]

Originally posted by: Born2bwire

Originally posted by: Finns14
I'm sorry I tried the methods you mentioned and they didn't work

Not much else to say at this point. You know the angles of a right triangle and you know the length of one of the legs of the triangle. From here it's just geometry.

Yeah, I don't know what to say either. You solve for one angle using Snell's law and then it's basic geometry from there. I would draw you a picture but I really don't feel like doing your homework for you.

 

[Nerva]

this is how you do it...

oh oh, i am done with college as of yesterday! fvck work!