Key relationship
1/q=1/f−1/d; a reciprocal plot has slope−1 and intercept1/f.
Physics · Practical apparatus
Convex-lens reciprocal plot
Obtain different sharp u-v pairs by moving the object and screen. Their reciprocals lie on a line. Reading the intercept provides another focal-length estimate.
Open the interactive experiment →Convex-lens reciprocal plot
பல தெளிவான u-v வாசிப்புகளின் தலைகீழ் மதிப்புகளை வரைந்தால் நேர்கோடு கிடைக்கும்.
Key notes, relationships and model limits
Practical tip
Obtain different sharp u-v pairs by moving the object and screen. Their reciprocals lie on a line. Reading the intercept provides another focal-length estimate.
Common trap
A single out-of-focus screen location is not an image-distance measurement.
Model limits
Thin convex lens, paraxial real-image measurements; only d>f provides a positive image reciprocal. Defocus guide requires screen at q.
What you will learn
Connect optical-bench pairs with a reciprocal straight-line plot.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
For f20 cm, intercept0.05 cm⁻¹; d40 gives q40 cm.
Why this matters
The model connects convex-lens reciprocal plot with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
The intercept of1/q versus1/d is?
- f
- 1/f
- −f
Read the explanation
Rearranging gives1/q=1/f−1/d.
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.