Photons & Wave-Particle Duality (OCR A Level Physics)

The Planck constant h is an important fundamental constant in quantum physics.

Determine the S.I. base units for h.

base units = .......................................

A researcher is investigating the de Broglie wavelength of charged particles.

The charged particles are accelerated through a potential difference V. The de Broglie wavelength λ of these particles is then determined by the researcher.

Each particle has mass m and charge q.

i) Show that the de Broglie wavelength λ is given by the expression 

[2]

ii) The researcher plots data points on a λ² against grid, as shown below.

1. Calculate the percentage uncertainty in λ for the data point circled on the grid.

percentage uncertainty = .................................... % [2]

2. Draw a straight line of best fit through the data points.

[1]

3. The charge q on the particle is 2e, where e is the elementary charge.

Use your best fit straight line to show that the mass m of the particle is about 10⁻²⁶ kg.

[4]