Paper 3a (Practical Skills)

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RP 01: Stationary Waves on a String

Equipment:

String

Meter ruler

Stand

Masses (100g) with holder

Vibration generator

Signal Generator

Wooden Bridge

Pulley

Balance

(Where length is the independent variable)

Method:

Set up apparatus

Take the string used and record its mass using a balance

Measure out a length of wire (1 meter), ensure that is the distance of wire between the generator and pulley.

Increase the frequency until the string oscillates at the first harmonic (2 nodes at each end and one antinode)

Record this frequency, f

Reduce the length of string in between the generator and pulley by intervals of 0.100m each time

Record the frequency for each length when the first harmonic is observed

Repeat until at a smaller interval e.g., 0.5

Repeat the whole process twice more to obtain mean values for f

Record the mass used on the pulley

Graphs & Calculation:

Plot a graph of the mean values for "f" against 1/length (l)

Draw a line of best fit

To calculate the tension, multiply the mass used (e.g., 400g) by the value for gravitational field strength (9.81)

To calculate mass per unit length just divide the recorded mass of the string by the length (e.g., 1.5m)

Safety:

The stand might topple, so you put a counterweight on the base

Improvements/ notes:

To investigate the effect of tension - change masses with each recording in intervals of 100g

To investigate the effect of mass per unit length - use increasingly thick string

Oscilloscope could be used to verify signal generator's readings

Signal generator should be left for around 20 minutes to stabilize

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RP 02: Young's slit & diffraction grating