A physics student investigates a glass convex lens that is advertised to have a focal…
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A physics student investigates a glass convex lens that is advertised to have a focal length of 30.0cm. She places the lens on an optical bench and measures the object distance so (from the object to the lens) and the image distance si (from the lens to the sharp image on a movable screen). Her measurements are recorded in the table below.
Trial
so (cm)
si (cm)
1
45.0
90.0
2
55.0
82.9
3
60.0
78.3
4
70.0
73.7
5
80.0
70.0
Assume sign conventions in which real object and image distances are positive.
(a) For each trial, determine the focal length of the lens in centimeters.
(b) Calculate the mean (average) focal length obtained from all five trials.
(c) Compute the percent difference between the mean focal length you found in part (b) and the manufacturer’s advertised value of 30.0cm. Show your work.
(d) Examination of the table shows a systematic trend in the calculated focal lengths as so increases. Identify whether the dominant error in this experiment appears to be random or systematic and justify your answer using specific features of the data.
(e) Propose two specific changes to the experimental procedure that could reduce the error you identified in part (d). For each proposed change, explain how it addresses the source of error.