This is a question about electromagnetic waves.
(a) State which colour in the visible spectrum has the shortest wavelength.
(b) Explain a hazard of ultraviolet radiation to the human body.
(c)(i) State the formula linking speed, wavelength and frequency of a wave.
(ii) Calculate the frequency of radio waves with a wavelength of \(15\,\mathrm{m}\).
[speed of light \(=3.0\times10^8\,\mathrm{m\,s^{-1}}\)]
Syllabus Topic Codes (Edexcel International GCSE Physics 4PH1):
(a) Shortest wavelength [1 mark]
The colour with the shortest wavelength in the visible spectrum is violet.
In the visible spectrum, wavelength decreases from red to violet.
(b) Hazard of ultraviolet radiation [2 marks]
Ultraviolet radiation can cause damage or mutations in cells, which can lead to skin cancer.
Prolonged exposure to UV radiation can damage body cells, particularly cells in the skin. UV radiation can also cause damage to the eyes, potentially leading to blindness.
(c)(i) Wave equation [1 mark]
The formula linking speed, wavelength and frequency is:
\(\boxed{v=f\lambda}\)
(c)(ii) Frequency of the radio waves [2 marks]
Rearrange the wave equation:
\(f=\dfrac{v}{\lambda}\)
Substitute the values:
\(f=\dfrac{3.0\times10^8}{15}\)
\(f=2.0\times10^7\,\mathrm{Hz}\)
Frequency: \(\boxed{2.0\times10^7\,\mathrm{Hz}}\)
