PHYSICS CONNECTION
A Planck-constant experiment needs uncertainty analysis
A graph can estimate Planck’s constant, but the reliability of the estimate depends on the voltage measurements and the gradient range allowed by them.
h = e × gradient of V against f
Follow the reasoning
- Plot the measurements with appropriate uncertainty bars.
- Draw a best-fit line and a justified worst acceptable line.
- Transfer the fractional gradient uncertainty to h.
OFFICIAL OCR QUESTIONS
Try it in a past paper 1
Open the question, then use its mark scheme to check your work.
Question 8
Use LED measurements and a graph to estimate Planck’s constant and its uncertainty.
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ORIGINAL PHYSICSUK QUESTIONS
Put the ideas to work
More practice is on its way
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Specification outcomes (4)
- 4.5.1(e)(i) Use LEDs and eV = hc / λ to estimate the value of Planck’s constant.
- 4.5.1(e)(ii) Determine Planck’s constant using different coloured LEDs experimentally.
- 2.2.1(a) Understand systematic errors (including zero errors) and random errors in measurements.
- 2.2.1(d) Use graphical treatment of errors and uncertainties, including line of best fit, worst line, absolute and percentage uncertainties, and percentage difference.