What are the immediate health effects of exposure to radiation?

What are the immediate health effects of exposure to radiation?
Exposure to moderate levels of radiation - above one gray - can result in radiation sickness, which produces a range of symptoms.
Nausea and vomiting often begin within hours of exposure, followed by diarrhoea, headaches and fever.
After the first round of symptoms, there may be a brief period with no apparent illness, but this may be followed within weeks by new, more serious symptoms.
At higher levels of radiation, all of these symptoms may be immediately apparent, along with widespread - and potentially fatal - damage to internal organs.
Exposure to a radiation dose of four gray will typically kill about half of all healthy adults.
For comparison, radiation therapy for cancer typically involves several doses of between one and seven gray at a time - but these doses are highly controlled, and usually specifically targeted at small areas of the body.

s.s.venkateshwar

Andaman