Which best describes external contamination with radiological material?

We speak of irradiation by external exposure to ionizing radiation, when a person is exposed from the outside by the ionizing radiation emitted by a radioactive source located in its vicinity (like the waste of the nuclear power stations or the remains of the explosion nuclear energy such as Hiroshima and Nagasaki). In this case, exposure ceases when the source of radioactivity is moved away from the person or if a screen (shielding) is interposed between the person and the source.
While a contamination by an internal exposure to radioactive particles, that is to say when radioactive elements have penetrated inside the organism, as in the case of ingestion e radioactive product as the iodine 131 in a diagnostic or therapeutic purpose.

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