Particles and Waves
Homework
Homework 1
1. The table below shows some of the relative sizes of some important objects.
Copy the table and fill in the missing size or object:
Particle or Object
Neutrino
Order of Magnitude
10-15 m
Hydrogen Atom
Dust
Human Being
107 m
Sun
1013 m
Galaxy
Distance to a Quasar
2. The physicist Ernest Rutherford conducted an experiment where Alpha
particles were fired towards a gold leaf within a vacuum. His results showed
that:
A.
Most alphas passed straight through without much deflection.
B.
Every so often an alpha was deflected through a large angle.
For each result, state what conclusion(s) were made about the structure of the
atom.
3.
(a) Describe what happens during beta decay.
(b) Measurements made during beta decay showed that the law of
conservation of momentum was being violated. Explain how these
observations lead to the discovery of the neutrino.
4. At present physicists believe there are 12 fundamental particles that make up
all mass, collectively known as Fermions:
Bottom
Top
Electron
Muon Neutrino
Up
Strange
Charm
Electron Neutrino
Muon
Down
Tau
Tau Neutrino
These 12 are split into two groups:
Leptons and Quarks.
(a)
Construct a table which sorts all 12 mass particles into their correct group.
(b)
Explain how scientists discovered the Neutrino through the study of Beta
decay.
(c)
For every mass particle there exists another particle which is identical but
has the opposite charge, what is the collective name given to these particles?
(d)
A Hadron is a particle made from a combination of quarks. There are two
types of Hadrons: Baryons and Mesons. State the difference between them.
(e)
Protons and Neutrons are both types of baryons. For each, state which quark
combinations each is made of and include information on the charges of these
quarks and the overall charge of:
(i)
the proton
(ii)
the neutron
5(a)
Copy and complete the following table of Gauge Bosons
Symbol

g
Z0
w
(b)
Name
Force carried
The particle responsible for carrying the ‘strong force’ is the gluon. What
distance range does this force act over?
Homework 2
1(a) Sketch the electric field lines expected from the following charged objects (must
include arrows).
2.
The potential difference between the anode and the cathode of an
electron gun is 20kV.
Calculate the speed of the electron when it reaches the anode.
3. An electron of mass 9.1 x 10-31 Kg and charge 1.6 x 10-19 C starts at rest
from an electrode charged up to - 8000 V towards an earthed plate.
(a) What is the potential difference the electron moves between?
(b) Calculate the work done on the electron by the field.
(c) What is the kinetic energy gained by the electron just before it hits the
plate?
(d) Calculate the speed of the electron just before it hits the plate
(e) How many electrons would need to pass to accumulate a
charge of 2.4 µC (2.4x10-6 coulombs) on the plate?
(f) If these electrons passed in 3 minutes, what would the current be?
4. The magnetic field drawn below indicates field lines coming out of the page.
(a) If an electron moved from the top
of the page to the bottom of the
page which direction would any
force act?
(b) In what direction would a
downward travelling positron
move?
(c) Copy the field diagram and mark
the track of the electron as it
passes through the field.
5.
An electron travelling at 2x107 m/s enters a magnetic field parallel to
the field
electron
Describe and explain the subsequent motion of the electron.
Homework 3
1.
Copy and label the diagram illustrating a fission reaction using the following
words and terms:
95
138
Ba
56
238
Kr
36
fission
U
92
neutron
neutrons
+
2.
(a)
fission products
energy
+
+ +
In a fission reaction the rest mass of the original particles was 3.91763 x
10-25Kg and the fission products had a rest mass of only 3.91397 x 10 -25
Kg.
Calculate the mass defect in the reaction.
(b)
Calculate the energy released in one fission reaction using a suitable
relationship
3.
(a) Copy and label the diagram of a fusion reaction using the following
terms and symbols:
2
2
H
H
1
1
+
3
He
2
neutron
fusion
+
+
energy
(b) Calculate the energy released during this reaction using:
particle
Mass (a.m.u.)
neutron
1.0087
Deuterium
2.0136
Helium 3
3.0149
Where a.m.u. stands for atomic mass unit and1 a.m.u. = 1.66 x 10 -27 Kg
4.(a) Which type of nuclear reaction, fission or fusion, takes place in the
Sun?
.(b) Describe the operation of a nuclear fission power station in less than
100 words.
(c) List two advantages and two disadvantages of nuclear power compared
to other energy sources.
Homework 4
1. Why was the photoelectric effect experiment done by Einstein important enough to
gain him a Nobel Prize?
2. What is the energy of a photon of light if the frequency of the light is8.6x1014Hz?
3. The work function of a metal is 6.4x10-19 J.
(a) Explain what is meant by the term ‘work function’.
(b) Light with a wavelength of 250nm is shone onto the metal surface.
(i) What is the frequency of the light?
(ii) Show whether or not the photons of this light will cause the
photoelectric effect to take place.
(c)The light source is now replaced with a light source which produces light
with a frequency of 1.5x1015 Hz.
(i)
The photons from this source contain more energy than is
required to release the electrons. How much extra energy is
available after the electron has been released?
(ii)
Into what energy type will this extra energy be converted?
4.
Sodium has a threshold frequency of 440 THz. A plate of clean sodium is
illuminated with radiation of frequency 620 THz, assuming each photon releases one
electron. Calculate:
A. The work function of the sodium.
B. The maximum kinetic energy of an electron released from the plate.
Homework 5
1. Why is interference important?
2. Explain why it is impossible to get an interference pattern from two light bulbs.
3.(a) What is meant by the term COHERENT?
(b) Explain the formation of the bright fringes in an interference pattern.
4.Calculate the wavelength of sound in each of the following diagrams:
(a)
(b)
LOUD
LOUD
10cm
LOUD
LOUD
60cm
LOUD
LOUD
30cm
LOUD
LOUD
50cm
LOUD
LOUD
5. The figure illustrates the interference of light:
Bright
(a) Explain the formation of the dark
fringes.
X
Bright
Bright
Bright
Bright
(b) If the light has a wavelength of
400nm calculate the path difference for
point X.
(c) What is the path difference for the
first order minimum?
Homework 6
1. A laser is incident on a grating as shown
Bright
Bright 2cm
laser
Bright
10cm
grating
Bright
Bright
(a) If the grating has 3000 lines per cm, calculate the wavelength of the light.
(b) What would be the effect on the pattern if a grating of 6000 lines per cm was used
instead?
2. A grating with a separation of 4x10-5m is used with light of wavelength 600nm.
Calculate the angle between the central fringe and the second maximum.
3. Light of wavelength 600nm is incident on a grating as shown
4
laser
0
grating
Calculate the line separation on the grating.
4. Describe two differences between spectra seen through a prism and the spectra
seen through a diffraction grating.
5. What colour is the central maximum when white light is shone through a grating?
Explain this.
Homework 7
1. Calculate the absolute refractive index in each of the following diagrams:
50
60
30
10
20
30
2. Calculate the unknown angle in each of the following diagrams:
n=1.5
x
n=2.1
40
x
30
3. Angles of incidence and refraction are measured for a glass block.
g
a
4(a). What is meant by
a. Describe how you could draw a
straight line graph with the results.
b. What is the gradient of your graph
equal to?
c. Describe three of the practical
difficulties with this experiment.
(i) critical angle
(ii) total internal reflection
(b) Calculate the critical angle for a material of refractive index (i) 2.2
(ii) 1.4
5. Light of wavelength 6x10-7m is incident on a glass block as shown
30
50
(a) Calculate the refractive index of the glass
(b) Calculate the critical angle
(c) Calculate the speed of light in the glass
(d) Calculate the wavelength of the light in the glass
(e) Calculate the frequency of light in the air
(f) What is the frequency of light in the glass?
Homework 8
1. A lamp has an intensity of 1000Wm-2 at a distance of 20cm from the source.
Calculate the irradiance at a distance of 50cm from the source.
2.
A solar cell measures 1cm by 5 cm and receives 400 mW of light from a small
light 50 cm away.
a. What is the irradiance on the cell?
b. What would the irradiance be :
(a)
1 m away?
(b)
2 m away?
c. Using suitable axes, sketch a straight line graph to show the relationship
between irradiance and distance from the centre of the lamp.
d. If the cell is 5% efficient, what power does it produce when placed 50 cm
from the bulb?
e. How close would it have to be to the bulb to produce 200 mW of power?
3. The intensity of laser light at a distance of 10cm from the source is 200Wm-2 . What
is the intensity at a distance of 20cm from the source? Explain your answer.
4. The diagram shows the energy levels in an atom
E3 -------------------------- -1.36x10-19 J
E2 -------------------------- -2.41x10-19 J
E1 -------------------------- -5.42x10-19 J
E0 -------------------------- -21.86x10-19 J
(a) How many transitions are possible?
(b) Calculate (i) the longest wavelength of radiation emitted
(ii) the shortest wavelength of radiation emitted
(iii) state which is most likely to cause the photoelectric effect
(c) In an emission spectra some colours are more intense than others.
Explain this observation.
5. In 1909 the New Zealand physicist Ernest Rutherford subjected a thin gold foil to
alpha particles. Carry out research to find out why:
- many of the alpha particles went straight through the foil
- some were deflected and a few ‘bounced’ back off the foil in the
opposite direction.
a. What two conclusions about the atom did these observations allow Rutherford
to infer about the size of the nucleus and the distribution of mass and hence
charge in the nucleus?
b. Sketch the model of the atom that these experiments supported.