Exam Questions (Redos, Techniques, Facts)

Question 1

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

In an experiment which involved measuring time, a student used a stopwatch - describe how different apparatus could be used to measure the time so that the % uncertainty is reduced

Answer 5

Either use a light gate and data logger for a more accurate determination of time
Or a video camera which can be analysed frame by frame

Question 7

Describe one safety precaution when carrying out the speed of stationary wave on string practical

Answer 7

Wear suitable footwear (to protect from falling masses)
Wear safety glasses (in case teh string breaks)

Question 8

When using a micrometer, give 1 technique for measuring stuff well

Answer 8

Look at the micrometer from different orientations along the wire
As the wire diameter may not be uniform
OR
Check for 0 error
As zero error reduces the accuracy of measurement

Question 9

When describing how a vibrating string causes pressure variations in the air: how do you describe how the molecules oscillate?

Answer 9

Molecules are displaced from equilibrium positions

Question 10

Never say antibodies have larger amplitude (when describing standing waves) instead say ____amplitude

Answer 10

Maximum

Question 11

Explain why waves need to be coherent to produce a standing wave

Answer 11

Coherent means the waves have a constant phase relationship
If the relationship is not constant, a point could be sometimes constructive and sometimes destructive

Question 12

Answer 12

Question 13

If the number of slits per mm in the diffraction grating increases, does d increase or decrease?

Answer 13

d = the slit separation
So it decreases

Question 14

REMEMBER WHAT when writing your final answer

Answer 14

Units

Question 15

What do you do to ensure accuracy of an experiment (increasing the likelihood of accuracy)

Answer 15

Decrease % uncertainty
(By increasing measumrent size or increasing resolution)

Question 16

Things with longer ___ diffract more

Answer 16

Wavelengths

Question 17

What is the unit of sin theta - how should you write the units for sin theta?

Answer 17

Sin (theta/little zero for degrees)

Question 18

How can you check whether a diffraction grating with a certain spacing is appropriate to measure d sin theta = n lambda?

Answer 18

There should be a significant difference in the angles for each of the maximas

Question 19

Answer 19

• diffraction occurs when light is reflected from the CD surface
• each ring on the CD acts as a diffraction centre scattering light in all directions
• interference occurs
• in directions in which there is a phase difference equal to an even multiply of pi radians (or a who,e number of wavelengths) there is constructive interference
• white light is a range of wavelengths
• each wavelength of light reinforces in a different direction which explains why a spectrum is seen

Question 20

Criticise these results

Answer 20

Inconsistent number of decimal places for resistance (resistance should be to 3dp)
Inconsistent intervals in temperature (large jump in temperature from 38 to 55)

Question 21

Should you include units for calculations of gradients?

Answer 21

Yes

Question 22

Give 3 things you could do to improve the accuracy of measumrents of your (y intercept) or (gradient)?
(Things in brackets would be replaced with the specific context of the question)

Answer 22

• take a measurement at 0 (with units) to measure (y intercept) accurately
• take (resistance) measurements for smaller increments (of temperature) - to improve accuracy of gradient
• use a digital (thermometer) - to avoid parallax error
• take (resistance) measurements for a wider range of (temperatures) - wider range of independent variable - to improve the accuracy of the gradient

Question 23

What two errors should you be careful to avoid when using a micrometer or vernier calliper

Answer 23

• check for zero error
• take readings in different orientations/positions

Question 24

Describe how a student can accurately determine the radius of the first bring ring/distance to maxima point of a diffraction pattern

Answer 24

• use vernier callipers
• measure the diameter of teh first ring and divide by 2 (or distance from first order maxima on left to maxima on right and divide by 2)
• measure in multiple orientations and calculate the mean
• measure to the middle/brightest part of the ring

Question 25

Explain how a diffraction pattern (showing concentric bright rings) gives evidence for the wave nature of electrons

Answer 25

• diffraction is a wave property
• the diffraction pattern is evidence the electrons have interfered

Question 26

When rearranging an equation into straight line form to explain why the line of best fit is a straight line what is it important to state

Answer 26

• that (the variables which are constants) are constants

Question 27

Explain how you could use a vernier callipers to measure the diameter of a coin accurately

Answer 27

• measure multiple coins / multiple positions/orientations on the same coin
  Mean diameter calculated
• check and correct for zero error of the measuring device

Question 28

Explain the variation of resistance with potential difference for the filament bulb in terms of particle behaviour

Answer 28

• as pd increases the energy of electrons increases
• so there is greater energy transfer in collisions with lattice ions
• increasing the temperature of the metal/filament/ions
• amplitude of vibrations of lattice ions increases
• collision rate between lattice ions and electrons increases
• due to the increase in resistance, the ratio of I/V decreases

NOTE the energy transfer being greater is a significant part of the answer!

Question 29

Add the missing sentence to this answer

Answer 29

Thermistor resistance as a proportion of total resistance decreases

Question 30

Answer 30

Question 31

Discuss the suitability of each circuit to collect the data

Answer 31

(Remember to write a statement in agreement if it asks you to discuss!)
- both circuits are suitable as they allow readings of pd/current for the lamp
- for circuit 1 the minimum pd across the lamp is 0V when the slider is on the left
- for circuit 1 the maximum pd across the lamp is the supply pd (when the slider is at the right)
- for circuit 2 adjusting the resistor changes the circuit resistance (so the current is varied)
- so for circuit 2 the minimum pd depends upon the resistance of the variable resistor
- circuit 1 is better because it allows a bigger range, and allows pds down to 0V to be used

Question 32

Answer 32

• the battery has internal resistance
• there is a pd across the internal resistance of the battery (lost volts)
• terminal pd is less than emf

Question 33

How should you edit the last sentence (instead of saying overheat) to get full marks on this question?

Answer 33

It reduces the life of the remaining bulbs

Question 34

To determine cross sectional area of a wire what equipment should you use

Answer 34

A micrometer

Question 35

You need a wire to make a 3 A fuse

If the actual maximum current of a fuse wire before it breaks is less than 3A does that make it suitable for use or not?

Answer 35

Yes