19: Exam Questions

Question 1

Which statement(s) is correct about nuclear fission? [1]
A: Total mass of the products of a fission reaction is greater than the mass of the nucleus undergoing fission
B: The avg. binding energy/nucleon of the products of the fission reaction is more -ve than the binding energy/nucleon of the nucleus undergoing fission
C: Energy is released in fission when low-mass nuclei join to make more massive nuclei
D: Uranium is the only element to undergo fission

Answer 1

B

Question 2

An electron in the lowest energy state in a hydrogen atom can be modelled as a standing wave equal to 4 times the radius of the atom
By considering how the potential energy and kinetic energy of the electrons vary with its distance from the proton, explain why a hydrogen atom has a minimum diameter (3)

Answer 2

Potential energy of electron is negative, kinetic energy positive
Kinetic energy of electrons increases with decreasing wavelength
…more quickly than potential energy becomes more negative
Atom unstable when k.e greater than p.e

Question 3

Polonium is a short lived radioisotope and produces a cascade of short lived isotopes. Explain why the gamma photons released during the cascade can be neglected when estimating the risk of cancer from the decays (2)

Answer 3

Gammas ionise less than alphas
Most gammas will pass through body
All alphas will be absorbed by small mass of tissue