In the question provided, the i angle is the one from the lamp in the water and the r is the one in the air.
What do you think about the answer I attached? Why is the r angle is the one in the water?!
Thank you very much for your reply.
Do you mean I don't put the meter rule over the pivot instead I put it on bench? The answer says the rule to be rule tilted and on bench!
Do you think it will be like this?
http://www.tiikoni.com/tis/view/?id=d5f23e3
Sorry I don't know how to use the template.
The question says the rule doesn't slip on the pivot but in the answer it says that to draw the rule tilted and in bench and to use suitable number of weight. How to do that?
[img=http://s29.postimg.org/3vvsylmaf/image.jpg]
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This is the answer for the question...
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http://postimage.org/][/PLAIN]
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The answer is saying the following,
initial reflection + 0 or 1 further reflection only, not at lower surface
must be straight and reach within 1cm of end.
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How come 0 or 1 reflection only ? The length...