YEAR 12 PHYSICS.
ASSIGNMENT #17.
Due Monday 3rd June
Q1. (a) How did Hertz discover the photoelectric effect? [1]
(b) What are photoelectrons? [1]
(c) Using a diagram, briefly describe what was meant by the “Ultraviolet catastrophe”. [3]
(d) What was Planck’s revolutionary explanation that explained the experimental results? [1]
(e) Identify the dependence of the release of photoelectrons on frequency. [1]
(f) Explain the problem classical physics had with explaining this dependence. [2]
(g) Describe the dependence of the kinetic energy of released photoelectrons on frequency. [1]
(h) According to experimental evidence, upon what did the numbers of released photoelectrons
depend? [1]
(i) What is the threshold frequency for a specific metal, in terms of the photoelectric effect? [1]
(j) How did Einstein explain the threshold frequency? [1]
(k) How did his theory explain the dependence of the photoelectrons’ K.E. on frequency? [2]
() Identify one use of the photoelectric effect, and explain how it works. [3]
Maximum K.E. [eV]
Q2.
(a) Consider this graph, which compares the
4
frequency of light falling on three metal
3
surfaces, A, B and C.
A
threshold frequencies of each metal. [3]
B
2
Identify the
C
(b) Which metal(s) emit photoelectrons if f =
15  1014 Hz; 3.0  1014 Hz; [2]
1
(c) What is the slope of these graph lines? [1]
0
10
25
15
20
30
(d) Why don’t the lines pass thro’ (0, 0)? [1]
frequency [ 1014 Hz]
(e) Use the graph to estimate Φ (the work function) for each metal. [3]
5
(f) Estimate the maximum K.E. of the photoelectrons from each of the metals if illuminated by
light photons having a wavelength of 3.0  10-7 m. [3]
(g) Use a diagram to explain how the maximum K.E. of the photoelectrons was determined. [2]
Q3. (a) Use a neat, labelled diagram to show the features of Rutherford’s gold leaf experiment. [4]
(b) Describe and explain the results Rutherford expected the experiment to produce. [4]
(c) What two experimental outcomes surprised Rutherford? [2]
(d) What did he conclude about atomic structure from each of these? Explain his reasoning. [4]
(e) Identify three reasons why the model he proposed seemed impossible. [3]