The graph shows details about a wave - Edexcel - GCSE Physics - Question 1 - 2018 - Paper 1

To find the frequency (f) of a wave, we can use the formula:

$f = \frac{v}{\lambda}$

Where:

• v is the wave speed (30 m/s)
• (\lambda) is the wavelength.

From the graph, the distance for one complete wave (the length of one cycle) is found to be 20 m. Thus, the wavelength (\lambda = 20 m).

Substituting the values into the formula:

$f = \frac{30\, \text{m/s}}{20\, \text{m}} = 1.5\, \text{Hz}$

So, the frequency of the wave is 1.5 Hz.

The focal length of a lens is defined as the distance from the lens to the focal point, where light rays that are initially parallel to the optical axis converge after passing through the lens. It is a measure of how strongly the lens converges or diverges light. A shorter focal length indicates a stronger lens.