Describing waves

4 marks · Normal

The following diagram shows a wave travelling along a rope.

Wave on a rope

(a)

Label the wavelength and amplitude on the diagram.

[2 marks]

(b)

Which point on this wave shows the maximum positive displacement from the equilibrium position? State its letter.

[1 mark]

(c)

What is the name of this maximum point?

[1 mark]

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

(a) Wavelength: horizontal distance from O to B or B to D labelled; Amplitude: vertical distance from O to A or O to C labelled. · must show Horizontal arrow from O to B (or B to D) with label 'wavelength', Vertical arrow from O to A (or O to C) with label 'amplitude'

(b) A

Must show: wavelength marked (horizontal distance from O to B, or B to D), amplitude marked (vertical height from O to A or O to C), A labelled as maximum positive displacement, crest named

Common mistakes: Labelling wavelength from O to D (should be from O to B or B to D); Labelling amplitude horizontally

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Wavelength arrow and label correctly shown (O to B or B to D).

B1 (a) · 1 mark · Amplitude arrow and label correctly shown (vertical from O to A or O to C).

B1 (b) · 1 mark · States point A as the position of maximum positive displacement.

B1 (c) · 1 mark · Names this point as a 'crest'.

Worked solution

a) Draw and label the horizontal distance from O to B (or B to D) as wavelength; draw and label the vertical line from O to A as amplitude.

b) The point with maximum positive displacement is A.

c) This maximum point is called a crest.