NCEA Level 3 Science (90732) 2007 — page 1 of 3
Assessment Schedule – 2007
Science: Describe selected properties and applications of EMR, radioactive decay, sound
and ultrasound (90732)
Evidence Statement
Note: Minor computational errors will not be penalised. A wrong answer will be accepted as correct provided there is
sufficient evidence that the mistake is not due to a lack of understanding. Such evidence includes:

the last written step before the answer is given has no unexpanded brackets or terms and does not require rearranging.
Question
Achievement
1(a)
High is where the lines are
closest, low is where the lines are
apart.
Both areas of High and Low
pressure clearly indicated.
1(b)(i)
Correct speed 322.5 m s–1 (with
correct working and unit).
1(b)(ii)
The frequency / pitch would be
lower.
1(c)
1(d)
The pitch drops at point B.
Energy (or amplitude) of the
sound wave reduces.
Achievement with Merit
Achievement with Excellence
 A to B. Higher pitch as sound
waves are compressed (shorter
wavelength or higher
frequency), due to the Doppler
effect.
 B to C. Lower pitch as sound
waves are stretched (longer
wavelength or lower
frequency), due to the Doppler
effect.
 A to B. Higher pitch as sound
waves have a shorter
wavelength or higher
frequency, due to the Doppler
effect.
 B to C. Lower pitch as sound
waves have a longer
wavelength or lower
frequency, due to the Doppler
effect.
ONE of the above.
BOTH of the above with a clear
link between wavelength and/or
frequency, and pitch.
 Sound reduces due to siren
being far enough away so that
less energy (or reduced
amplitude) reaches the ears as
sound spreads out away from
the source.
 Energy from the sound wave
gets absorbed by objects and
the air to reduce the amount of
energy reaching the ear.
 Energy is dispersed over a
larger area as the car moves
away reducing the energy
reaching the ear
ONE of the above.
NCEA Level 3 Science (90732) 2007 — page 2 of 3
1(e)

The kidney has a softer
surface and reflects less of the
ultrasound.
The kidney stone has a harder
surface and reflects more of
the ultrasound.

ONE of the above needed.


The kidney has a softer surface
and reflects less of the
ultrasound, which takes less
time for the ultrasound to
reflect and be detected by the
scanner.
The kidney stone has a harder
surface and reflects more of
the ultrasound, which takes
more time to be detected by the
scanner.
ONE of the above explained.
2(a)
Neutron decays into a proton,
while emitting a beta particle
(electron).
ALL particles required.
2(b)
-1
0
β (e)
and
14
7
N
(One error allowed.)
2(c)
(Average) Time taken for half the
isotope (mass of isotope in
sample, or count rate of sample) to
decay.
NOT the mass of the sample.
2(d)
Correct shape.
2(e)
One sixteenth = 4 half-lives.
Age = 4  5 750 years
= 23 000 years old.
(Clear answer from labeled
extrapolation of the graph is
acceptable.)
2(f)




Tree is too old.
Tree size is too small.
Contamination.
Not enough C-14 in the wood
for accurate dating
 The ratio of C-14 in the
atmosphere may have changed
over time
ONE of the above correct.
3(a)(i)
Three incoming parallel rays
reflect off the dish to accurately
converge at a focus.
3(a)(ii)
Radio receiver labeled at the
focus.
Includes correct values at
T = 0, 5 750, 11 500 and
17 250 years, and correct shape.
A correct explanation outlined.
Eg: The old age of the tree means
that only a small amount of C-14
will be left in the wood sample.
The small amount of C-14 within
the sample could be contaminated
by C-14 within the dust.
NCEA Level 3 Science (90732) 2007 — page 3 of 3
3(b)
V=dt t=dv
= 4.2  1010 m
3.0  108 m s–1
= 140 s.
Correct answer and unit.
3(c)
ONE point about radar AND ONE
point about visible light from:
 Radar can be transmitted
through the atmosphere / clouds
of Venus.
 Radar reflects from the surface
of Venus.
 Visible light is absorbed by the
atmosphere, so that it doesn’t
reach the surface.
A link shown between radar and
visible light such as:
Radar is transmitted through the
atmosphere / cloud and then reflects
from the surface of the planet.
Some light is absorbed by the
cloud / atmosphere and some is
reflected off the surface of the
cloud / atmosphere.
 Visible light reflects from the
surface of the atmosphere /
clouds.
3(d)
c=fλ λ=cf
= 3  108 m s–1
9.5  109 Hz
= 0.032 m / 0.0316 m
(3.2 cm or 32 mm)
An answer fully linking all the
points in the Achievement answer,
such as:
 Radar is transmitted through the
atmosphere / cloud and then
reflects back from the surface of
the planet which is transmitted
back through the cloud /
atmosphere to the receiver.
Some light is absorbed by the
cloud / atmosphere and some is
reflected off the surface of the
cloud / atmosphere and back to
the receiver.
Correct working, sensible answer
(2sf) and unit.
Correct answer and (unit).
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
NINE opportunities answered at
Achievement level or higher.
TEN opportunities answered with at
least FOUR at Merit level or higher.
ELEVEN opportunities answered with
at least ONE at Excellence level and
FOUR at Merit level.
9A
4M+6A
1E+4M+6A