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You need to be well-acquainted with the IB command terms (Physics Guide, 2023) and phrases listed in this section. Each command describes an expected action, on the basis of which the mark scheme is designed. We will actively use them through this course.
State
State
Give a specific name, value or other brief answer without explanation or calculation.
State what is meant by a transverse wave. [1]
the displacement/oscillation is at right angles/perpendicular to the direction of energy transfer/propagation ✔
Accept vibration/movement of particles for oscillation.
Explain
Explain
Give a detailed account including reasons or causes.
Explain whether P or Q has the greater acceleration. [3]
P and Q are performing SHM ✔
«in SHM» acceleration is proportional to displacement so P ✔
acceleration is a maximum at P AND zero/minimum at Q ✔
MP2 can be expressed as an equation.
Outline
Outline
Give a brief account or summary.
Outline how the central maximum is formed. [3]
diffraction occurs/light diffracts «at each slit» ✔
light arrives «from each slit» at central max in phase/path difference to central max is zero ✔
constructive superposition/interference takes place ✔
For MP2 do not allow general statements of phase/path difference e.g. 2π or integer number of wavelengths. Question asks about central maximum.
Describe
Describe
Give a detailed account.
The suspension unit is repaired so that the spring is damped. Describe any changes that the person will notice when riding over the same bumpy ground. [4]
less/reduced amplitude of vibration ✓ resonant frequency lower ✓ resonance occurs at lower speed ✓ oscillations die out (faster) ✓
Draw / Model
Draw / Model
Represent by means of a labelled, accurate diagram or graph, using a pencil. A ruler (straight edge) should be used for straight lines. Diagrams should be drawn to scale. Graphs should have points correctly plotted (if appropriate) and joined in a straight line or smooth curve.
The light ray is partly reflected from the glass–water boundary. Draw, on the diagram, the path of the reflected ray. [1]
ray at a correct angle by eye to the normal ✔
Estimate
Estimate
Obtain an approximate value.
Estimate the amplitude of the resultant wave. [1]
8.0 OR 8.5 «μm» ✓
From the graph on the paper, value is 8.0. From the calculated correct trig functions, value is 8.49.
Calculate
Calculate
Obtain a numerical answer showing the relevant stages in the working.
Calculate the fraction of the kinetic energy of the bottle that remains after the bounce. [2]
Attempt to evaluate KE ratio as (v-final/v-initial)^2 ✓ « =» 0.20 OR 20 % OR 1/5 ✓ Accept ± 0.5 velocity values from graph
Show
Show
Give the steps in a calculation or derivation.
Show that the period of the oscillations is about 0.7 s. [3]
Predict
Predict
Give an expected result.
The student changes the light source to one that emits two colours: blue light of wavelength λ, and red light of wavelength 1.5λ. Predict the pattern that the student will see on the screen. [3]
Blue fringe is unchanged ✓ Red fringes are farther apart than blue ✓ By a factor of 1.5 ✓ At some point/s the fringes coincide/are purple ✓
Determine
Determine
Obtain the only possible answer.
The slits are separated by a distance of 0.18 mm and the distance to the screen is 2.2 m. Determine, in m, the wavelength of light. [2]
Discuss
Discuss
Offer a considered and balanced review that includes a range of arguments, factors or hypotheses. Opinions or conclusions should be presented clearly and supported by appropriate evidence.
The student moves the screen closer to the double slit and repeats the measurements. The instruments used to make the measurements are unchanged. Discuss the effect this movement has on the fractional uncertainty in the value of λ. [2]
«As the measurements decrease» the fractional uncertainty in D/s increases. ✓ «Fractional uncertainties are additive here» so fractional uncertainty in increases ✓ Answers can be described in symbols e.g. Δs/s
Source: International Bacculerate Orgnization, Physics Guide (2023)
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