1. ## Prisms question

Hi can anyone help me answer this question

Construct a triple tangent scale for use at 2.5 metres on which you could read thepower of an unknown prism in prism dioptres, degrees of deviation and degreesof apical angle (assume a refractive index of 1.523)  Reply With Quote

2. I think the gist of it is you have to do a science project.

Like, get a piece of cardboard and put it 2.5M from a prism sitting on a table (maybe base down).

Shine a beam of light through it. Like a cool laser! But you'd need "collimated light" I think, so get out the optical bench.

Measure the deviation from dead center.

Then use math to calculate prism diopters and degrees of deviation, and then plug and chug into the formula that includes the apical angle (which I only vaguely remember).

Good luck!

Oh, what's a triple tangent scale? I can see how one would use trigonometry, here, but they're looking for you to devise a scale to read on the cardboard that you could maybe answer all three questions (apical angle, degrees, p.d.) for any prism you'd put in there.  Reply With Quote

3. When I googling for a tangent scale I came across this https://www.speedwaydelhi.com/produc...ent-scale.html
Which could be used to measure prism, but I doubt that's called a triple tangent scale as it's only in 2 axes, maybe the 3rd axis is an object that measures/controls distance since you would need a way to convert the distance to 1m to properly measure prism.  Reply With Quote

4. ## Tangent scale - hope it helps, even thou its 2 years too late! Originally Posted by SDO Hi can anyone help me answer this question

Construct a triple tangent scale for use at 2.5 metres on which you could read thepower of an unknown prism in prism dioptres, degrees of deviation and degreesof apical angle (assume a refractive index of 1.523)

You need to create a scale with the three requirements mapped out such that when viewed through the prism the image will be moved to the corresponding value - or if the scale is lined up at zero then the laser will point to the correct value.

use X=PY to find the size of each section, where X = the section size, P= prism power (use 1d for calculations) and Y = the distance from the scale, remember X will be in metres if Y is in metres.

you can then use P=100.tan(D) for the deviation and D=(n-1).A for the apicle angle.  Reply With Quote

5. "then use math" Awesome.  Reply With Quote

6. It's very useful.  Reply With Quote

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