refraction

HI All,

I hv question but no mark scheme - hope someone can help.

It relates to the classic light beam going into a glass block with Incident and refraction angles.

There is a graph of angle of refraction vs angle of incidence.

The plot is not a straight line [a straight line would be from sin(i) and sin(r) graph].

It seems it's not a very common graph to plot as I cant find that many online compared to sin(i) sin(r).

The question is
what 2 conclusions can be made about the relationship between the angles of incident and the angle of refraction from the graph.

[this line is apparently fairly straight for small angles, then curves for the rest of the line.]

(edited 10 years ago)

Reply 1

krisshP

Original post by RMIM

I'll try my best

Where angle of incidence>glass block critical angle. Hence total internal reflection occurs, meaning angle of incidence=angle of reflection. Here no refraction occurs. So for this reason there's no angle of refraction, meaning the graph doesn't exist here. However after you decrease the angle of incidence, the angle of incidence will=glass book critical angle. At this point light will simply travel along the glass boundary, meaning that the angle of refraction=90*. You could say that the graph begins here since it is where an angle of refraction first exists. If you decrease angle of incidence further, angle of refraction decreases and eventually becomes zero.

This might help
http://t3.gstatic.com/images?q=tbn:ANd9GcSu9d1kkC0qg35QYX5lmSVVYczh-qrBTuvpsUCTxKPXrsFBVKop

Reply 2

RMIM

Original post by krisshP

I'll try my best

Thanks for the reply kriss - I'm not sure if this is what the question is asking.
I will attach the actual question perhaps that will make things clearer.

refraction graph.pdf34.4KB

Reply 3

krisshP

Original post by RMIM

Thanks for the reply kriss - I'm not sure if this is what the question is asking.
I will attach the actual question perhaps that will make things clearer.

Not entirely sure, sorry. Do you do AQA? Just found this which might help you
http://www.google.com/url?sa=t&rct=j&q=what%20two%20conclusions%20can%20be%20made%20about%20the%20relationship%20between%20the%20angle%20of%20incidence%20and%20the%20angle%20of%20refraction%20from%20graph%201%3F%20aqa&source=web&cd=7&ved=0CDkQFjAG&url=http%3A%2F%2Fwww.thepolesworthschool.com%2Fdepartments%2Fscience%2Fsciencerevision%2Fy10%2FAQA%2520Physics%2520P1%2520past%2520paper%2520questions%2520with%2520MSCHEME%2520set%2520A-1.doc&ei=wSKVUdOTO4jS0QXlmoDoAg&usg=AFQjCNGGW4hY9WwWgELr41JkSC8UdodDQg&sig2=ufu7HoqqmVZM5U_oFfC-Ew&bvm=bv.46471029,d.d2k
Its full of questions and answers

Try finding the mark scheme for the question paper that refraction question is on.

Reply 4

RMIM

Original post by krisshP

Try finding the mark scheme for the question paper that refraction question is on.

Thanks for that. Not sure if it's there, but it's useful stuff.

there is a similar question with the anser

the angle of incidence increases, the angle of refraction increases
or there is a (strong) positive(non-linear) relationship between the variables

I think that would get you 1 mark - what else can we conclude?

(edited 10 years ago)

Reply 5

krisshP

Original post by RMIM

Unsure

Reply 6

2^1/2

for part a,

google images search for Snell's law graph

for b, you should be able to work out the refractive index contrast of the materials using snells law (and a plot of sin i vs sin r), also critical angle (as above). The question I believe is just wanting you to say it is non-linear, and shows (stong) positive correlation.

(edited 10 years ago)

Reply 7

RMIM

Original post by 2^1/2

Thanks for the help I believe that could be it

mark 1. Non-linear
mark 2. Positive correlation

Although 'non-linear positive correlation' could be just one line and 1 Mark?

(snells law is not on the syllabus)

I hate not having the mark scheme.

(edited 10 years ago)

Reply 8

2^1/2

Original post by RMIM

I agree, it asks for two things, which could be non-linear, and a positive correlation. My other thought would be you could say: angle of incidence > angle of refraction (which would mean the light is going into a material of higher refractive index than it came from), otherwise can't say much about the graph.

Apologies for mentioning snells law, but it's always interesting to push yourself a bit, and you already knew it really knowing about taking the sine of the angles.

Hope that's useful

Reply 9

RMIM

Original post by 2^1/2

Yes I was thinking that myself (angle of incidence > angle of refraction) but then I was thinking is that a bit too simplistic? - looking at it again as you brought it up, I think it's a valid conclusion - as it does tell you about the refractive index being higher, again perhaps we should use the word more dense material as I don't think even refractive index in on the syllabus, but more dense material is.

I'm trying to stick to the syllabus to try and get the answers they are after.

Thanks for the help 2^1/2, I think you cracked it.