The reasons why 241am smoke detectors are perfectly safe is because;
(i) The amount of americium is very little.
(ii) The aluminium core is where the detector is hosted.
(iii) The detector has a plastic cover.
(iv) Radiation is limited in penetrating power.
(v) There is a low number which is leaving the case.
(iv) ions get trapped by electrodes.
Answer:
pfu/ml
Explanation:
Given -
Bacteriophage dilution
ml
Volume of bacteria and plate with top agar
ml
Number of plaques
pfu
Dilution (d) 
Final concentration of phage stock is equal to

Where pfu is the count of plaques
d is the dilution and v is the volume
Substituting the given values, we get -
pfu/ml
Answer:
Sty I have not learned this yet hopefully i will next year