I/GCSE Physics Question Analysis Topic: Physics - Short Questions
Exam Questions:
1) Define the activity of a given radioactive substance. Write its S.I units.
2) Explain with the help of a circuit diagram the working of a photo diode. Write briefly how it is used to detect the optical signals.
Answers:
For I/GCSE Physics, you should know:
1) The rate at which a radioactive material is decaying is known as its activity.
Becquerel is the SI unit of activity (Bq).
2) A photodiode is a junction diode made of a light-sensitive semiconductor.
A photodiode is an electrical device that uses a photo detector to detect light and transform it into an energy signal.
The way a pn-junction works is determined by the light that reaches it.
Let's suppose that the wavelength is such that the energy of a photon hv / λ is enough to break a valence bond. When this happens, the number of charge carriers increases which thus increases the conductivity of the junction. Should the junction be connected in a circular configuration, the intensity of the incident light would control the circuit's current.
Circuit diagram:
Work hard for your I/GCSE Physics examination!
End of analysis. Great!