All: Paper 1 Flashcards
State what is meant by ionisation.
Ionisation is the removal (or addition) of electrons from (to) an atom or molecule
Use your knowledge of physics to explain why a smoke detector containing
americium-241 (B- Decay) does not provide any risk to the user.
- Only a small quantity of material is needed
- The particles it emits do not travel more than a few centimetres
Outline how the student can use these results (graph) and other measurements to
determine the Young modulus of the wire.
- Measure original length and diameter
- Determine gradient of linear section to obtain F/extension
- YM=FL/Ae
An engineer redesigns the crane to lift a 1200kg load (originally 600kg) at the same maximum
acceleration.
Discuss the changes that could be made to the cable of the crane to achieve this,
without exceeding 0.20% strain.
-To lift double the load at the same acceleration, would require double
the force
-To produce the same strain either use:
• double the cross-sectional area of the wire/increase the
diameter by √2 – so the stress stays the same and therefore
the strain is the same for the same wire
• a wire with double the Young modulus – so that double the
stress produces the same strain for the same diameter
The wooden block is replaced by a steel block of the same mass. The experiment is repeated with the steel block and an identical pellet. The pellet
rebounds after striking the block. Discuss how the height the steel block reaches compares with the height of 0.63m reached by the wooden block. In your answer compare the energy and momentum changes that occur in the two experiments.
- As pellet rebounds, change in momentum of pellet greater and therefore the change in momentum of the block is greater
- Initial speed of block is greater (mass stays the same)
- Initial KE of block greater
- Therefore height reached by steel block is greater than with wooden block
Describe the structure of a step-index optical fibre outlining the purpose of the core and the cladding.
- Core is transmission medium for em waves to progress (by total internal reflection)
- Cladding provides lower refractive index so that total internal reflection takes place
- And offers protection of boundary from scratching which could lead to light leaving the core.
Suggest an experiment that will demonstrate the wave nature of sound.
Suitable experiment eg diffraction through a door/out of a pipe
‘The procedure involved timing the interval
between seeing the flash of a gun and hearing the bang from some distance away.
Gassendi assumed that, compared with the speed of sound, the speed of light is
infinite’.
Explain why it was necessary to assume that ‘compared with the speed of sound, the speed of light is infinite’
Measured time is difference between time taken by light and time taken by sound
Calculation assumes that light takes no time to reach observer, ie speed is infinite
Explain one observation that could have led Gassendi to conclude that ‘the speed of sound does not depend on frequency’
- Sound from gun is a mixture of frequencies.
- All the sound reaches observer at the same time
‘A much better value of 350 ms−1 was obtained by the Italian physicists Borelli and
Viviani using the same procedure’. ‘Since 1986 the accepted value has been 331.29 ms-1’.
Explain how the value obtained by Borelli and Viviani was ‘much better’ than that obtained by Gassendi.
More accurate, as it is closer to the accepted value.
State the steps taken by the scientific community for the value of a quantity to be
‘accepted.
- The method and value are published
- Other scientists repeat the experiment using the same method
Explain how energetic electrons cause the atoms of the vapour of an element to emit light.
Outer electrons of the vapour atoms are excited when an energetic electron collides with it, transferring energy to the orbiting electron. The excited electron de-excites back to the ground state, emitting a photon.
How does the existence in the spectrum of lines of a definite wavelength support the view that atoms have discrete energy levels?
The energy of a photon depends on the wavelength of the light. The discrete wavelengths suggest that the atom only has specific fixed energy states.
