Life is like riding a bicycle.  To keep your balance you must keep moving.”
Albert Einstein

Thursday, January 14, 2010

Geometric Optics- A Free Response Practice Question for AP Physics B

The essential points to be remembered in geometric optics were discussed in the post dated 29th December 2007. You can access all posts related to geometric optics by clicking on the label ‘geometric optics’ below this post.

Today I give you a free response practice question in this section:

The figure shows a thin converging lens of focal length 12 cm. A small object O (indicated by a vertical arrow) is placed on the principal axis of this lens at a distance of 10 cm from the optic centre of the lens.

(a) Making use of at least two rays proceeding from the object, draw a ray diagram showing the image formed by the lens.

(b) Comment on the nature of the image: whether it is real or virtual; magnified or diminished; erect or inverted.

Justify your comment.

(c) Another thin converging lens of focal lens 20 cm is kept in contact with the above lens so that they have a common principal axis. The object O is kept at 10 cm itself from the centre of the combination of these lenses. Calculate the distance of the image (formed by this combination) from the centre of the lens system, making use of the law of distances.

(d) Is the image formed in this case real or virtual? Justify your answer.

Try to answer the above question. You can take about 11 minutes for answering it and can score up to 10 points for the right answer. I’ll be back shortly with a model answer for you.

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