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An approximate value of the Planck constant h can be determined in the laboratory using light-emitting diodes (LEDs) - OCR - A-Level Physics A - Question 20 - 2018 - Paper 1
Question 20
An approximate value of the Planck constant h can be determined in the laboratory using light-emitting diodes (LEDs). An LED suddenly starts to conduct and emit mono... show full transcript
Worked Solution & Example Answer:An approximate value of the Planck constant h can be determined in the laboratory using light-emitting diodes (LEDs) - OCR - A-Level Physics A - Question 20 - 2018 - Paper 1
Step 1
Draw the straight line of best fit on Fig 20.1
Answer
To draw the line of best fit, observe the data points plotted in Fig. 20.1. The line should follow the general trend of the points, ensuring it minimizes the distance to all points. Once the line is drawn, ensure it has a non-zero y-intercept and reflects the correlation between V_0/V and \frac{1}{\lambda} (in m^{-1}).
Step 2
Determine the gradient of the line
Answer
To calculate the gradient, select two points on the line of best fit. Let the coordinates of Point 1 be (x_1, y_1) and Point 2 be (x_2, y_2). The gradient (m) is calculated using the formula:
where y_1 and y_2 are the values of V_0/V and x_1 and x_2 are the corresponding values of \frac{1}{\lambda}.
Substituting the chosen points, you will obtain the gradient value, which is approximately 1.3 \times 10^{4} Vm.