Edexcel IAL Physics Unit 3 WPH03 May June 2016 Discussion

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Reply 40

Hamadtype-

Original post by Blazyy

I put in parallax error when placing the pins, is that also correct?

ummmmm, what do you mean by pins?

Reply 41

Ali Bizri

Original post by Hamadtype-

My gradient was 5, my resistivity was 1.23*10^-6

Exact same :biggrin:

What did you write for the "comment on safety" for the refractive index experiment?

Also for the how to find refractive index question i wrote
Refractive index = Sin I / Sin r
Take a reading of angle of incidence and refraction from the graph
Multiply them by sin and divide to find refractive index

Is that correct?

Reply 42

Blazyy

Original post by Blazyy

I put in parallax error when placing the pins, is that also correct?

Nevermind, ignore my question

Reply 43

don't cry-craft

Original post by Ali Bizri

Exact same :biggrin:

I put: draw a graph of sin 1 against sin r and calculate the gradient which will give you the refractive index. For safety, I said don't point the ray box towards yours and others' eyes as the laser can damage your eyes,

Reply 44

don't cry-craft

Original post by Blazyy

Nevermind, ignore my question

If you mean put the pins along the refracted ray, then yeah it makes sense that there would be a parallex error there.

Reply 45

Hamadtype-

Original post by Ali Bizri

Exact same :biggrin:

For safety I wrote low voltage

but for refractive index calculation they asked for graphical calculation, so you had to say draw a graph of sin i on sin r and find gradient

Reply 46

Sunethra

Original post by Hamadtype-

Yeah, But the second and third point was out of the best fit line

I got a value of 4.91 fr gradient! :/

Reply 47

Ali Bizri

Original post by don't cry-craft

That makes sense, the answers should be identical for both methods so I don't think it'll be a big deal, for safety i said that this is a low risk experiment and i added one more point which was the risk of falling block so wear foot protection.

Reply 48

don't cry-craft

Original post by Hamadtype-

Parallax error for protractor lol :biggrin:

how can there be a parallax error since the protractor would be flat against the paper to measure the angle?

Reply 49

Sunethra

Original post by Hamadtype-

For safety I wrote low voltage

but for refractive index calculation they asked for graphical calculation, so you had to say draw a graph of sin i on sin r and find gradient

What did you write to "comment on her plan" when she measured the time as 3s for a trolley to go down a slope?

Reply 50

Hamadtype-

It should be on your eye level horizontally , like you need to make your eyes directly parallel to the measurement, some people can stand away from the protractor and count.

Reply 51

Hamadtype-

Original post by Sunethra

What did you write to "comment on her plan" when she measured the time as 3s for a trolley to go down a slope?

I wrote there would be human reaction time error, so an electronic timer would be better for accurate results.

Reply 52

Sunethra

Original post by Hamadtype-

It should be on your eye level horizontally , like you need to make your eyes directly parallel to the measurement, some people can stand away from the protractor and count.

I said parralex errors when using protractor and I said other rays might be incident on the glass block so in brackets I said do the experiment in a dark room

Reply 53

don't cry-craft

Original post by Hamadtype-

I wrote there would be human reaction time error, so an electronic timer would be better for accurate results.

yeah same, especially since 3s is a very short amount of time.

Reply 54

iWant.A

Original post by Sunethra

What did you write to "comment on her plan" when she measured the time as 3s for a trolley to go down a slope?

I measured the persentage uncertainty by doing 0.38/3 *100 and found about 12.5% and commented that it is too high

Reply 55

don't cry-craft

Original post by Sunethra

I said parralex errors when using protractor and I said other rays might be incident on the glass block so in brackets I said do the experiment in a dark room

Oh okay, I said that there's an uncertainty of 0.5 degrees when taking the readings, especially since the angles can be quite small. Would this be okay?

Reply 56

Suhaib.134

Guys my value for resistivity was 4.6x10^-6? i think i did something wrong when finding the area of the wire but my gradient was 4.5? i thing im out of the range of what they would expect

Reply 57

jannz

hey my exam was good. is the graph supposed to be a straight line or a curvy type of thing.
if i used the right method to find gradient and the value of resistivity but got the wrong answer will i get any marks.

Reply 58

Blazyy

Original post by Hamadtype-

ummmmm, what do you mean by pins?

Sometimes when you don't have a ray box in hand, you use pins to mark the incident and refracted ray.

Reply 59

Hamadtype-

Original post by Suhaib.134

Guys my value for resistivity was 4.6x10^-6? i think i did something wrong when finding the area of the wire but my gradient was 4.5? i thing im out of the range of what they would expect