Electromagnetic waves, which include light, consist of vibrations of electric an

Question

Electromagnetic waves, which include light, consist of vibrations of electric and magnetic fields, and they all travel at the speed of light.

a) Sunburn (and skin cancer) is caused by ultraviolet light waves having a frequency of around 1.05×1016 Hz . What is their wavelength? Express your answer in nanometers to three significant figures.

b) It has been suggested that extraterrestrial civilizations (if they exist) might try to communicate by using electromagnetic waves having the same frequency as that given off by the spin flip of the electron in hydrogen, which is 1.46 GHz . To what wavelength should we tune our telescopes in order to search for such signals? Express your answer in centimeters to three significant figures.

Explanation / Answer

Here .

a) frequency = 1.05 *10^16 Hz

wavelength = speed of wave/frequency

wavelength = 3 *10^8/(1.05 *10^16)

wavelength = 2.857 *10^-8 m

b)

frequency = 1.46 GHz = 1.46 *10^9 Hz

wavelength = speed of wave/frequency

wavelength = 3 *10^8/(1.46 *10^9 )

wavelength = 0.205 m

the telescopes should be tuned to 0.205 m = 20.5 cm

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