Experimenting with a Concave Mirror and a Candle

[jnimagine]

we used a concave mirror and a candle for an experiment
when the candle wa placed between the vertex and the focus of the mirror (f=12.7cm) a virtual image appeared behind the mirror.
We measure the image distance approximately by pointing a finger towards where the image might be and got 6.0cm (-6.0 when used in mirror equation) and the object was at 6.35cm. However, when I use the mirror equation to calculate the focus, i get a negative answer that is not even close to the actual focus 12.7cm. Do u think this is just due to human errors of not measuring the image distance accurately or is there some other factors that can account for this? OR is the image distance supposed to be almost the same as the object distance in this case?

 

[andrevdh]

Yes, the virtual image did form at -12.7 cm according to the formula (which do work by the way!).

Locating a virtual image by parallax (or by finger as you say) can be tricky. Especially if you do not know what you are actually doing and did not had a bit of practice.

So I would think that you did not succeed too well at pointing at the correct position behind the mirror, that is you had to hold your finger two times futher backwards.

 

[kyle8921]

I would say that there are a few factors that could potentially account for the discrepancy between the measured and calculated focus in this experiment.

Firstly, it is possible that there were some human errors in measuring the image distance accurately. It is important to be precise and careful when conducting experiments, as even small errors can have a significant impact on the results.

Secondly, the mirror equation assumes certain ideal conditions, such as a perfectly spherical mirror and a point source of light. In reality, these conditions may not be met, which could also contribute to the discrepancy between the measured and calculated focus.

Lastly, it is important to consider the concept of parallax when measuring the image distance. Parallax refers to the apparent shift in position of an object when viewed from different angles. In this experiment, pointing a finger towards where the image might be could introduce some parallax error, leading to an inaccurate measurement of the image distance.

To address these potential factors, it would be beneficial to repeat the experiment multiple times and take multiple measurements to ensure accuracy. Additionally, using more precise tools such as a ruler or measuring tape could also improve the accuracy of the measurements. Overall, it is important to carefully consider and control all variables in an experiment to obtain reliable and accurate results.