Physics
Electric fields and radioactivity
- 1.
Parallel plates have a potential difference of 600 V and separation 0.020 m. Assume a uniform field. Calculate its magnitude and the magnitude of the force on a charge of +2.0 microcoulombs.
[3 marks] - 2.
A detector reads 820 counts per minute initially and 120 counts per minute 6.0 hours later. Background is constant at 20 counts per minute. Assuming exponential decay, find the sample's half-life.
[4 marks] · no calculator - 3.
A metal has work function 2.0 eV. Light of wavelength 400 nm falls on it. Use h = 6.63 x 10^-34 J s, c = 3.00 x 10^8 m s^-1 and 1 eV = 1.60 x 10^-19 J. Find maximum photoelectron kinetic energy in eV and stopping potential. Explain whether doubling intensity changes stopping potential.
[4 marks]
Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.