Some amount of a radioactive substance (half-life=10days) is spread inside a oun and consequently ,the level of radiation becomes 50 times the permissible level for normal occupancy of the room.After how many days,the room will be safe for occupataion?

Radon is a radioactive gas with half-life 56 s.For health reasons,the maximum permissible level of radon in air in a building is set a t 1 radon atom for every .15xx10^(21) molecules of air 1 mol of air in the building is contained in 0.024 m^3 .Calculate ,for this building the maximum permissible number of radon atom in 1.0 m^3 of air

Radon is a radioactive gas with half-life 56 s.For health reasons,the maximum permissible level of radon in air in a building is set a t 1 radon atom for every .15xx10^(21) molecules of air 1 mol of air in the building is contained in 0.024 m^3 .Calculate ,for this building the number of molecules for air in 1.0 m^3 .

A cobalt-60 source having a half-life of 5.27 years is calibrated and found to have an activity of 3.50 xx 10^5 Bq.The uncertainty in the calibration is +- 2% .Calculate the length of time.in days, after the calibration has been made, for the stated activity of 3.50 xx 10^5 Bq to have a maximum possible error of 10%.

Radioactive disintegration is a first order reaction and its rate depends only upon the nature of nucleus and does not depend upon external factors like temperature and pressure. The rate of radioactive disintegration (Activity) is represented as -(dN)/(dt)=lambdaN Where lambda= decay constant, N= number of nuclei at time t, N_(0) =initial no. of nuclei. The above equation after integration can be represented as lambda=(2.303)/(t)log((N_(0))/(N)) Half-life period of U is 2.5xx10^(5) years. In how much time will the amount of U^(237) remaining be only 25% of the original amount ? a) 2.5xx10^(5) year b) 1.25xx10^(5) years c) 5xx10^(5) years d) none of these

A radioactive material is reduced to 1/16 of its original amount in 4 days. How much material should one begin with so that 4 xx 10^(-3) kg of the material is left after 6 days.

Upon irradiating californium with neutrons, a scientist discovered a new nuclide having mass number of 250 and a half-life of 30 min. After 90 min. of irradiation, the observed radioactivity due to nuclied was 100 dis/min. How many atoms of the nucliede were prepared intially? a) 2.4xx10^(4) b) 3.46xx10^(4) c) 1900 d) 800