If you can remember your answers please post them here.
1. Particles
a. What is particle X, udd (1 mark)
Neutron
b. What is the interaction (1 mark)
Weak interaction
c. What group of particles does W- belong in? (1 mark)
W bosons
d. What is the most stable baryon? (1 mark)
Proton
e. What are the decay products of a muon?
muon neutrino, electron, anti-electron neutrino
f. Show how charge and baryon number are conserved in this interaction, making reference to quarks.
Neutron ---> Proton + electron + anti-electron neutrino
charge before: udd = +2/3 -1/3 -1/3 = 0
charge after: udu + electron + anti-electron neutrino = +2/3 -1/3 +2/3 -1 +0 = 0
Baryon number before: udd = +1/3+1/3+1/3 = 1
Baryon number after: udu + electron + anti-electron neutrino = +1/3+1/3+1/3+0+0 = 1
2. Electricity
a. Why is the graph of a filament lamp a curve with regard to the electron motion? (4 marks)
Resistance is very low at first, therefore there is a high current. As the voltage increases, the filament heats up, the electrons and ions vibrate more, this makes it more difficult for ions to move. Therefore the resistance increases and current is low.
b. resistance of the resistor
15 Ohms
c. What is the resistance of the filament in series to the resistor when the current is 0.18?
14.5
d. What is the resistance of the filament in parallel to the resistor when the EMF is 4V?
6.25
3.
4. Forces and Motion
a. Show the power output is 100W (2 marks)
Travels 12km at 1.5m/s, therefore in 8000seconds. Using Q = It, find the current. Then use P= IV. Power was 108W, which is approximately 100W
b.
c.
d. Resistive force
72N
e. How do these factors affect the maximum range? (4 marks)
Mass: higher mass decreases the range
Speed: higher velocity increases the range
5. Young's double slit
Maximum intensity. Why is the minimum frequency between C-D (minima) not 0?
Intensity is about the number of photons arriving per second, therefore does not affect frequency.
6. Stationary waves
a. Show that the extension of the wire is less than 4mm (2 marks)
Extension was 3.125mm
b. Calculate the necessary tension in the supporting ropes so that the there is no horizontal resultant force acting on the cable.
c. Calculate the frequency of a stationary wave formed on the cable when at the third harmonic.
Use the first harmonic equation
7.4 or 7.5
d. Drawing of third harmonic on wire
4 nodes including at the fixed points, 3 antinodes
e. Explain how stationary waves are formed on the cable when it is windy, and why only certain wavelengths are possible.
f. Why does the copper wire sag when there are strong winds?
Strong winds cause a larger amplitude of the waves, therefore a larger extension. The wires suffers from plastic deformation.
7. Fluorescent tube
a. Which is an evidence for the wave nature of an electron? (1 mark)
C - Diffraction rings
b. What is the state of 0? (1 mark)
Ionisation state
c. What is the state -13.7eV? (1 mark)
Ground state
d. Why are the values negative below 0?
e. Energy of photons with the lowest wavelength of light?
1.9ev
f. Why does the fluorescent tube need a high pd supply? How does the energy level diagram show the wavelengths of light in the spectrum. Which one wavelength corresponds to 2 energy levels? (6 marks)
A high pd supply means that the free electrons in tube become fast moving free electrons, therefore collide with mercury atoms. This causes excitation and ionisation. De-excitation emits UV photons. UV absorbed by atoms on the fluorescent coating, causing excitation. De-excitation of coating atoms emit visible light photons. The energy level diagrams show the de-excitation of the electrons in in the coating atoms. The quantum jump shows the energy of the photon emitted. This can be used to find the wavelength of the photon.
Total number of marks: 70