Alpha radiation is used in smoke detectors.
Weak sources of the radiation are put inside the detector near two electrodes. The alpha radiation ionises the air inside of the detector, which causes a current to flow between the electrodes.
If theres a fire the smoke absorbes the radiaton. This stops the flow of current, which consiquently sounds the alarm.
Tracers in Medicine
Beta and Gamma particles are used as tracers in medicine.
The radioactive isotopes can be swallowed or injected into the body, and their activity inside of the body can be monitoured using a detector. Computers convert the readings of the detector into a display that shows where the strongest reading is coming from.
A common example of this is iodine-131. Its absorbed by the thyroid gland and gives out radiation thats detected to see whether the gland is taking in iodine like it should.
The isotopes that are taken into the body must always be gamma or beta, so that the radiation passes out of the body.
Gamma rays are used in radiotherapy, which is the treatment of cancer.
High doses of gamma rays can kill iving cells, which means that they can be used to treat cancers. The rays are directed at the cancer cells at the right dosage, and are rotated around the patient to minimalise the damage to healthy cells.
Inevitably some damage is done to the healthy cells, which can make the patients ill. If the cancer is treated though its worth it.
Gamma rays can be used to sterilise food and surgical equiptment.
When food is exposed to high dosages of gamma rays the microbes on it are killed, which keeps the food fresh for longer. Medical instruments are sterilised in the same way.
This method of sterilisation is better than bioling because it doen't need to be done at high temperatures, so things can be sterilised properly without being damaged.