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Physics Form 4 Answers
3. (a) d = v × t = 1500 × 0.18 (ii) • There is resistance a particle of the medium
= 270 m between the loaded spring vibrates/oscillates but
(b) The depth of the sunken ship and the oil. [1] does not move along with
= d = 270 = 135 m • As a result, energy is lost the wave. [1]
from the system as heat
2
2
2
(c) Ultrasonic waves have more energy. [1]
energy than audio waves. • If no external force is applied, 7. (a) • The convex-shaped peak of
the spring will eventually the wave is like a convex lens.
4. (a) P = X-rays stop completely. [1] [1]
Q = Infrared • Damping. [1] • The light rays from the lamp
(b) (i) 100.6 × 10 Hz or 4 passing through the peak will
6
1.006 × 10 Hz (d) (i) be converged on the screen to
8
produce a bright band.
(ii) Wavelength • The trough is like a concave [1]
= 3.0 × 10 8 lens. [1]
1.006 × 10 8
= 2.98 m. • The light rays from the lamp
passing through the trough will
(c) For taking the image of the [1] be diverged causing a dark
patient’s bones. • Move the hand band. [1]
to-and-fro, perpendicular 4
5. (a) (i) High frequency sound to the spring. [1]
waves. • The waves move forward (b) (i) • The frequencies of the
(ii) • Ultrasonic waves along the spring. [1] waves in both the deep
transmitted by the bat is • The string tied to the and shallow areas are the
reflected by the body of spring which represents same. [1]
the bird. a particle of the medium • The wavelength of the
• The reflected waves is oscillates perpendicularly waves in deep area is
detected by the bat. to the direction of the longer than that in shallow
• The time between waves. [1] area. [1]
the transmission and • This shows that in • The speed of the waves
detection of the signal by the propagation of a in deep area is higher
the bat is equal to twice transverse wave, the than that in shallow area.
the distance between the particle of the medium [1]
bat and the bird. vibrates/oscillates (ii) • When the angle of
• With that, the distance perpendicularly with the incidence is zero, the
between the bat and the direction of the wave. [1] direction of waves
bird can be estimated moving from deep to
through the period of Max 4 shallow areas remains
time transmission and (ii) unchanged. [1]
detection of the ultrasonic • When the angle of
waves. incidence is not zero,
(b) (i) Distance = d m [1] the waves change their
2d = 1 450 × 120 × 10 . direction when moving from
-3
Therefore d = 87 m. • Move the hand to-and-fro, deep to shallow areas. [1]
parallel with the spring. [1]
(ii) v = fλ • The waves move forward 5
1 450 = 45 × 10 × λ along the spring. [1] (c) Refraction of waves [1]
3
1450 • The string tied to the
Therefore, λ = (d) (i) • The resort is to be built
45 × 10 3 spring which represents near the bay [1]
= 3.2 × 10 m a particle of the medium • The waves at the bay are
-2
oscillates parallel with the
Section B direction of the waves. [1] calmer than at the cape [1]
6. (a) A system that undergoes a • This shows that in • due to the divergence of
periodic to-and-fro movement. [1] the propagation of a the waves’ energy from
(b) • Spring B carries a bigger longitudinal wave, the the bay [1]
mass than that of spring A. [1] particle of the medium • and the convergence of
• Spring B oscillates with a vibrates/oscillates parallel the waves at the cape [1]
bigger period than spring A. [1] with the direction of the (ii) • To reduce erosion,
• Spring B oscillates with a wave. [1] retaining walls are built [1]
lower frequency compared to Max 4 • to reflect the waves from
spring A. [1] the shore [1]
• The bigger is the mass (iii) • Work done by the hand in • and to reduce direct
attached to the spring, the moving the spring impact of the waves on
lower is the frequency of its to-and-fro causes the the shore [1]
oscillation. [1] energy to be transferred (iii) • Concrete structures with
a gap in between are built
4 in the form of waves at the designated area for
(c) (i) Oscillating with the along the spring. [1] children [1]
amplitude decreasing with • The string tied to the • Waves passing through
time. [1] spring which represents
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ANS FOC PHYSICF F4 1P.indd 260 29/01/2020 2:04 PM
