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AISSCE 2016 Physics Question Paper feedback

How was the CBSE Physics exam?
When the question was asked to teachers and students the response was a mixed one.

Not as expected

Time was not enough
Question paper was lengthy
1 and 2 marks questions were easy
Five marks questions were confusing

Etc … were some of the reactions
How do you feel?
How was the paper?

Respond now. Your response counts. It will also help the teachers and Principal to take up the matter to CBSE authorities.

 

Feedback Received

Very Easy but Very Lengthy

“I appeared yesterday for the respective exam. It was quite surprising for us to see the very easy Physics Exam! I myself had prepared hard for it but the exam was much lengthy especially 3 marks questions. I myself couldn’t attempt 10 marks which i had already realized were quite easy questions. But I  have to accept this disappointment now” – Shubham Dhingra

How to find the focal length of convex mirror using convex lens?

How to find the focal length of convex mirror using convex lens?

Asked Manisha

Answer:

We cannot use an optical method to determine the focal length of a convex mirror without using a convex (converging) lens since a convex mirror does not form a real image of an object in front of it or even parallel rays coming from infinity.

Therefore we have to use a convex mirror to determine the focal length of the convex mirror by an indirect method.

STEP 1 DETERMINE THE ROUGH FOCAL LENGTH OF THE CONVEX LENS

First of all we take a convex lens and determine  its rough focal length by forming a real image of a distant object on a screen. The distance between the convex lens and the screen gives the rough focal length, since when the object is at infinity, the image formed by the convex lens is at its focus. This method is called the distant object method to estimate the focal length of a convex lens. The focal length of a concave mirror may also be estimated using this method.

Experiment for focal length of convex lens

Now, as we know the approximate focal length of the convex lens, keep an object- an optical pin or a lit candle in front of the convex lens at a distance around 2 times the rough focal length determined and place a screen on the other side so as to form a real image of the object on it. This adjustment is done so as to make the distances involved quite manageable.

When you get a clear and sharp image on the screen, mark the positions of the convex lens and the screen on the table.

Place the convex mirror in between the screen and the lens without disturbing the position of the candle and the lens.

Place the screen close to the candle. Carefully adjust the position of the convex mirror alone so that you get a sharp image on the screen which is now kept  at the position of and along with the candle. Mark the position of the convex mirror now.

The distance between the position of the convex mirror and the old position of the screen gives the radius of curvature of the convex mirror. (Since r = 2f; we can determine the focal length by dividing the distance with 2)

Why the distance is r (2f)?

We know that when a ray of light is incident normally on the surface of a mirror, it retraces its path.

We also know that a line drawn from the centre of curvature of the mirror to the surface of a mirror is normal to the surface.

Therefore, when we are getting the image at the same position as the candle, it is formed by retracing of the rays, which means that the old position of the screen is at the position of the centre of curvature of the convex lens.

Read the post

http://www.askphysics.com/focal-length-of-convex-mirror-using-convex-lens/

See the Videos below to understand how the focal length of a convex mirror is determined using a convex lens in an optic bench.
https://youtu.be/-G1Yp1Nszmo

CBSE Physics – Semiconductors concept map, question bank and value based questions

Semiconductors concept map

Download (PDF, 400KB)

Semiconductors Question bank

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Semiconductors value based question bank

Download (PDF, 153KB)

CBSE Physics – Optics concept map, question bank and value based questions

Optics Concept map

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Optics question bank

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Optics value based questions

Download (PDF, 42KB)

CBSE Physics – Electromagnetic Waves Concept map, question bank and value based questions

Electromagnetic Waves Concept map

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Electromagnetic Waves Graded Question Bank

Download (PDF, 87KB)

Electromagnetic Waves Value based questions

Download (PDF, 78KB)

Download AISSCE 2015 CBSE Physics Board Question Paper and solution

You can now Download AISSCE 2015 CBSE Physics Board Question Paper and solution HERE

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CBSE Published Date Sheet for AISSCE 2016

Download the AISSCE (CBSE Class XII Board Exam)  2016 Time Table here

CBSE-SENIOR SCHOOL CERTIFICATE EXAMINATION DATE-SHEET-2016

Tuesday, 01 March, 2016 10.30 A.M.

001 ENGLISH ELECTIVE

101 ENGLISH ELECTIVE-C

301 ENGLISH CORE

Thursday, 03 March, 2016 10.30 A.M.

054 BUSINESS STUDIES

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