# Homework Help: Question on Optics, finding images of a pin using a concave mirror

1. Nov 4, 2011

### Krishna0703

A pin AB, 1cm long, is placed at an angle to the principal axis in front of a concave mirror, of focal length 5cm. Point B lies on the principal axis at a distance of 4 cm. Point A is such that the angle ABP is 60°, where P, the pole, is the point where the principal axis intersects the mirror.

a.) Find the positions of A' and B' of the needle's image.
b.) Determine the image's nature and magnification.

I have attempted to the solution but still i feel am in a sort of foolish mistakes...would be grateful if anyone can help me please. after going through the physics, i am sure and convinced that the image is an erected, magnified and virtual now...and obtained magnification as 3. part a.) of the question is unsure...can u help with an answer please...

2. Nov 4, 2011

### ehild

Hi, Krishna,

Can you show a picture, and your work, please? You must be on the right track, as the image is virtual.

ehild

Last edited: Nov 4, 2011
3. Nov 4, 2011

### Krishna0703

sure...i will take a snap of it and share it here..can u download the files plz..then u zoom on it for better view...sorry for the scrap i written...but am a poor student...that already embarrasses me

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4. Nov 4, 2011

### ehild

Is the magnification not defined as the seize of the image divided by the seize of the object ?

I do not see if you did anything to find the image of A. See my drawing.
What is the object distance for the red object? Note, that the length of the pinl=1 cm. Find the position of A' and determine the length A1B' to get the magnification.

ehild

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5. Nov 4, 2011

### Krishna0703

can u help me with a work solution for this time please?

6. Nov 5, 2011

### ehild

I do not understand what is a work solution you expect from me. I am just trying to help. The point A is at the peak of the red arrow in my previous picture. Determine the position and size of the image of the red arrow: Its peak is the image of A.
For that, you need the object distance, do, it is shorter than it was for B. Therefore, the magnification will be different for A and B.

ehild

7. Nov 5, 2011

### Krishna0703

okki, i got it, am off to my desk to work it out ehild..thanks.