AQA ยท A level Physics

Single-ion electromagnetic field mapping challenge

Can you get 100%? Use one trapped beryllium ion to test electric force, resonance and how repeated measurements build a three-dimensional field map.

Read how one ion maps fields above a chip

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Question

8 marks

Answer all parts. Show your working and give units where appropriate.

1(a)

A singly charged ion is placed in an electric field of strength 1.0 x 10^-8 V m^-1. Calculate the magnitude of the electric force on the ion. Use elementary charge e = 1.60 x 10^-19 C.

[2 marks]

1(b)

The ion is held in a trap and has a natural oscillation frequency. An alternating electric field is varied through this frequency. Explain how resonance makes the ion a sensitive detector of the field.

[3 marks]

1(c)

The ion is moved to many known positions above the chip. At each position the experiment measures static displacement, resonant heating and shifts of quantum energy levels. Explain why these measurements can separate different field components and form a three-dimensional map.

[3 marks]

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