Transcript Today`s Objectives - RanelaghALevelPhysics

Nuclear Radius
Nuclear Physics
Homework

Research and explain how electron diffraction
can be used to determine the radius of the
nucleus (6 Marks)

Past Paper Question on today’s material.
Complete both by Next Lesson, next Monday,
Period 5.

Learning Objectives



State and use the equation for dependence of
radius on nucleon number.
Calculate nuclear density.
Recall the implications of the high nuclear
density compared to atomic density.
Equation

Dependence of radius on
nucleon number:-
R  r0 A
1/ 3
[The term A1/3 means the cube root of A, the nucleon
number. The term r0 is a constant with the value 1.4 × 10-15
m. R is the nuclear radius.] What physical quantity is r0?
Rearrange in the form of A=.
Try working out R for Gold (A =197 ) and Carbon (A=12)
Nuclear Density


Radius of a carbon nucleus ~ 3.2 x 10-15m.
Radius of a gold nucleus ~ 8.1 x 10-15m.

Mass of a carbon nucleus ~ 2.00 x 10-26kg.
Mass of a gold nucleus ~ 3.27 x 10-25kg.

What are the densities of the nuclei?

Nuclear Density





Density of carbon nucleus ~ 1.46 x 1017 kg m-3.
Density of gold nucleus ~ 1.47 x 1017 kg m-3.
Very high! One teaspoon = 500 million tonnes.
So pretty much the same, regardless of element.
Ext: Work out mass of neutron star based on
this density. How does it compare to solar mass?
Nuclear Density

Nuclear density >> Atomic Density

This implies:Most of an atom’s mass is in its nucleus.
The nucleus is small compared to the atom.
An atom must contain a lot of empty space.



Example Exam Questions





Q1:
(a)If a carbon nucleus containing 12 nucleons has a
radius of 3.2 x 10-15m, what is r0?
(b) Calculate the radius of a radium nucleus containing
226 nucleons.
(c) Calculate the density of a radium nucleus if its mass
is 3.75 x 10-25 kg.
Q2: A sample of pure gold has a density of 19300 kg m3. If the density of the gold nucleus is 1.47 x 1017kg m-3
discuss what this implies about the structure of a gold
atom.
Learning Objectives



State and use the equation for dependence of
radius on nucleon number.
Calculate nuclear density.
Recall the implications of the high nuclear
density compared to atomic density.