Grade 12 phy

Half-life of a radioactive element is 30 days, then the remaining amount after 90 days

• 1/3

• 1/4

• 1/8

• 1/16

Which electromagnetic waves are mainly used as a treatment for cancer?

• alpha rays

• x rays

• beta rays

• gamma rays

• radio

• a) 920 MeV

• 1.6 MeV

• 920 MeV

• 1.6 MeV

• 270 MeV

A radioactive isotope A decays to B which decays to C, and C decays to D as represented by the figure below

                   A  ----^α--->   B   ----^β---->  C   ----^α---->  D

      What is the change in the mass number from A to D?

• It is decreased by 9 

• It is decreased by 6 

• It is decreased by 5.  

• It is decreased by 9

• It is decreased by 8.  

A sample of uranium-238 contains 2.50 × 10²³ atoms. Given that the half-life of uranium-238 is 1.42 × 1019 seconds. What is the decay constant λ, and the activity of this sample, respectively?

• 4.88 x 10²⁰/s and 1.2 x 10⁴ Bq

• 2.06 x 10²⁰/s and 1.2 x 10⁴ Bq

• 3.04 x 10²⁰/s and 2.6 x 10⁴ Bq

• 2.06 x 10²⁰/s and 0.8 x 10⁴ Bq

• 4.88 x 10²⁰/s and 0.8 x 10⁴ Bq

. Which statement about alpha, beta and gamma radiation is correct?

      

• Alpha radiation has the greatest ionizing power.

• Beta radiation has the greatest ionizing power.

• Gamma radiation has the greatest ionizing power.

• Alpha, beta and gamma radiation have nearly equal ionizing powers.

Which are the correct descriptions of a γ-ray and a β-particle, respectively?

• γ- high-speed electron, and β- electromagnetic radiation

• γ- electromagnetic radiation, and β- 4 Helium nucleus

• γ- electromagnetic radiation, and β- high speed electrons

• γ- high-speed electron, and β- 4 Helium nucleus

Which of the following statements is true for nuclear forces?

• They are forces between charges.

• They obey the inverse third power law of distance

• They are short range forces

• They are equal in strength to electromagnetic forces

After three half-lives, how much of a sample will remain radioactive?

• 1/2

• 1/4

• 1/8

• 1/3

• 1/6

________ is a nuclear reaction in which a heavy nucleus is split into two or more smaller and lighter nuclei after being bombarded by fast-moving neutron.

• Radiaactive decay

• Nuclear fusion

• half-life

• Nuclear fission