Waves
5 marks · NormalA student investigates different types of waves in a science laboratory. She uses a slinky to create waves. She also looks at an electromagnetic spectrum chart displayed in the lab.
State the difference between a transverse wave and a longitudinal wave. Give one example of each type from the student’s investigation or from the electromagnetic spectrum.
Identify one quantity and its unit that the student would measure when describing any wave in the lab.
Describe what is meant by a wavefront, using the slinky or water surface as examples.
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(a) Transverse waves vibrate at right angles to direction of travel (e.g. light, waves on a slinky shaken sideways); longitudinal waves vibrate parallel to the direction of travel (e.g. sound, slinky pushed and pulled).
(b) Frequency, measured in hertz (Hz), or wavelength (metre, m), or speed (m/s), or time (s), or angle (°).
(c) A wavefront is a line where all points on a wave are at the same phase/part of the vibration. In water, it is seen as the crest of the ripple; for a slinky, it is a region moving down the spring with all coils vibrating together.
Common mistakes: Mixing up transverse and longitudinal direction; Incorrect units; Weak wavefront explanation
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states difference between transverse and longitudinal waves.
B2 (a) · 1 mark · Gives one appropriate example of each type.
B3 (b) · 1 mark · Identifies relevant physical quantity and its correct unit (e.g. hertz, metre, m/s, second, degree).
B4 (c) · 1 mark · Defines or describes 'wavefront' clearly (same phase/vibration).
B5 (c) · 1 mark · Example or contextual reference (water, slinky, surface).
Worked solution
a) Transverse waves vibrate at right angles to the direction of travel; longitudinal waves vibrate parallel to the direction of travel. For example, water waves or light are transverse; sound waves or a slinky pushed and pulled are longitudinal.
b) Frequency (hertz, Hz), wavelength (metre, m), speed (m/s), time period (second, s), or angle (degrees, °) are all measurable quantities.
c) A wavefront is a line or surface connecting points with the same phase of vibration, like the crests seen on a ripple tank surface or the sections of a slinky moving together.