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A student carried out an experiment to measure the focal length of a concave mirror - Leaving Cert Physics - Question 2 - 2020
Question 2
A student carried out an experiment to measure the focal length of a concave mirror. (i) Draw a labelled diagram of the apparatus used in this experiment. (ii) Sta... show full transcript
Worked Solution & Example Answer:A student carried out an experiment to measure the focal length of a concave mirror - Leaving Cert Physics - Question 2 - 2020
Step 1
Draw a labelled diagram of the apparatus used in this experiment.
Answer
To illustrate the apparatus for measuring the focal length of a concave mirror, create a diagram that includes:
- A concave mirror, clearly labeled.
- An object (such as a crosswire or an arrow) placed in front of the mirror.
- An image or a screen where the image is formed.
- Include the optical bench and a ray box to provide context.
- Ensure correct arrangement where incident rays from the object strike the mirror.
- Label each component clearly, emphasizing their function.
Step 2
State the formula used to calculate the focal length.
Answer
The formula to calculate the focal length (f) of a concave mirror is given by: rac{1}{f} = rac{1}{u} + rac{1}{v} where:
- is the object distance (distance from the object to the mirror).
- is the image distance (distance from the image to the mirror).
Step 3
On your diagram, indicate and label the measurements taken by the student.
Answer
In the diagram, indicate the following measurements:
- Label the distance , which is the distance from the object to the mirror.
- Label the distance , which is the distance from the image to the mirror.
- Ensure both measurements are clearly marked and correctly referenced to the respective object and image.
Step 4
Step 5
Why did the student measure the approximate focal length at the start of the experiment?
Answer
The student measured the approximate focal length at the start of the experiment to ensure that the object was placed correctly within the focal length range of the concave mirror. This is critical for obtaining a real image, which is necessary for accurate measurements during the experiment.
Step 6
The image distance is the less accurate measurement. Explain why.
Answer
The image distance is considered the less accurate measurement because it can be difficult to precisely locate the sharpest point of the image. This point is where the light rays converge to form a clear image, and minor variations in positioning can lead to significant differences in the measured distance. Moreover, environmental factors such as vibrations and imperfections in the image formation can further affect measurement accuracy.