OLevel Physics Lens Question, please answer quickly!! :(

[Anonymous321]

The syllabus states
''draw scale diagrams to determine the focal length
of a converging lens needed for particular values of
magnification''

How do we do this!
And please read the question carefully before you answer.

 

[FLRNAB]

The syllabus states
''draw scale diagrams to determine the focal length
of a converging lens needed for particular values of
magnification''

How do we do this!
And please read the question carefully before you answer.

1) Light rays parallel to the Principal Axis will get refracted and go through the focal point and vice versa:

2) I think you would be given the lengths and you will just use those lengths to draw ray diagram and figure out the focal length as the rays would go through the focal point.
3) Just to make sure your answer is correct or near:

 

[Anonymous321]

1) Light rays parallel to the Principal Axis will get refracted and go through the focal point and vice versa:

2) I think you would be given the lengths and you will just use those lengths to draw ray diagram and figure out the focal length as the rays would go through the focal point.
3) Just to make sure your answer is correct or near:

FLRNAB Y U SO AWESOME!

but hey, the equation isn't part of the syllabus right?

 

[Anonymous321]

Also, do u have a sample question related to this? from Past papers or anywhere...

Hey and can you explain what optical pins are used for in refraction experiments? like what is the point in using them? I dont get it

Edit: I made a question on my own, solved for the focal length. Then implemented values in formula to check. It was correct (0.1cm ka difference though)

 

[FLRNAB]

FLRNAB Y U SO AWESOME!

but hey, the equation isn't part of the syllabus right?

I do the same as you follow the syllabus. Just remember the equation and write it down in the morning, evening and night so it will get stuck in your brain.

Also, do u have a sample question related to this? from Past papers or anywhere...

Hey and can you explain what optical pins are used for in refraction experiments? like what is the point in using them? I dont get it

Edit: I made a question on my own, solved for the focal length. Then implemented values in formula to check. It was correct (0.1cm ka difference though)

Woh scale ki wja sy hamesha aaye ga.

For understanding:

Using Pins:
1) Place glass on paper and draw it's outline. Draw Normal
2) Push a pin in the paper and mark it's angle of incidence.
3) Look at curved surface of the prism until you see the pin. Push another pin there so it coincides with the image of the incident pin :/

 

[Anonymous321]

I do the same as you follow the syllabus. Just remember the equation and write it down in the morning, evening and night so it will get stuck in your brain.


Woh scale ki wja sy hamesha aaye ga.

For understanding:

Using Pins:
1) Place glass on paper and draw it's outline. Draw Normal
2) Push a pin in the paper and mark it's angle of incidence.
3) Look at curved surface of the prism until you see the pin. Push another pin there so it coincides with the image of the incident pin :/

I.DONT.GET.IT!. I'M SO DUMB

 

[Anonymous321]

I mean, are we relying on what WE see through the glass block, cx we don't have a ray box? WAAAAAAAT?

Edit: I tried to understand this. What I've been able to wrap my head around (AND DON'T JUST SAY ''YA YA YOU'RE RIGHT'' WITHOUT READING THIS) is that the optical pins are being used as markers to draw line once we've switched the ray box off? But why can't we just draw line ON the rays then? And why are we looking THROUGH the protractor/glass prism thingie?

 

[FLRNAB]

The pins wala part, i.e. I mean, are we relying on what WE see through the glass block, cx we don't have a ray box? WAAAAAAAT?

Yes.
http://www.tamdistrict.org/cms/lib/CA01000875/Centricity/Domain/551/Refraction Lab.pdf

 

[Anonymous321]

Read the edit too, plis?

 

[FLRNAB]

Read the edit too, plis?

You misunderstood me completely. That raybox was to give you some kind of intuition. In the experiment you won't have ray box. You have to rely on seeing the image and placing the pins.

 

[Anonymous321]

I think I get it now 0.O that pdf is helpful

 

[Anonymous321]

hmmmm yea I get it now : D Did u go into depth with Cameras and Slide Projectors and Photo Enlargers?

 

[FLRNAB]

hmmmm yea I get it now : D Did u go into depth with Cameras and Slide Projectors and Photo Enlargers?

No. I didn't do them.

 

[Anonymous321]

No. I didn't do them.

They're part of the syllabus, though.

There's a question in ATP that requires us to ensure that the focal length of a lens is 15 cm (2009 ka paper)
What I wrote; since an object at 2F (2 X focal length) forms an image at 2F, too
we'll place an object at a distance 30 cm (15 X 2) from the lens. If the distance of the image form the lens is 30cm, too, then the focal length is 15 cm : )

You think they'd accept this? There's no mention of this in the Examiner's Report or MS. PEOPLE ARE STUPID!

Is this even correct?

 

[FLRNAB]

They're part of the syllabus, though.

There's a question in ATP that requires us to ensure that the focal length of a lens is 15 cm (2009 ka paper)
What I wrote; since an object at 2F (2 X focal length) forms an image at 2F, too
we'll place an object at a distance 30 cm (15 X 2) from the lens. If the distance of the image form the lens is 30cm, too, then the focal length is 15 cm : )

You think they'd accept this? There's no mention of this in the Examiner's Report or MS. PEOPLE ARE STUPID!

Is this even correct?

Link to paper? Also ask in the physics thread. You will get faster responses.

 

[Anonymous321]

I don't wanna waste my time reading inaccurate answers or things like ''I dont know'' with sad smilleys : /


http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w09_qp_4.pdf
Q3 in this paper

 

[FLRNAB]

I don't wanna waste my time reading inaccurate answers or things like ''I dont know'' with sad smilleys : /


http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_w09_qp_4.pdf
Q3 in this paper

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.

Your answer is correct as well and the same in procedure as ms answer but it is a unnecessarily longer as in measurement "processing"
Faizan Muhammmad

 

[Anonymous321]

On the contrary, I find this a much shorter answer. And easier to demonstrate via a diagram. Plus, it MAKES SENSE TO ME

 

[Faizan Muhammmad]

This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of
the examination. It shows the basis on which Examiners were instructed to award marks. It does not
indicate the details of the discussions that took place at an Examiners’ meeting before marking began,
which would have considered the acceptability of alternative answers.

Your answer is correct as well and the same in procedure as ms answer but it is a unnecessarily longer as in measurement "processing"
Faizan Muhammmad

Mainay kia karna hai ?

 

[Faizan Muhammmad]

for that first part all you have to do is put it such that sun's image is formed on screen
it will be focused at 15 cm
that is it