1. Visible light and microwaves are electromagnetic waves used for communication.
a) Name two properties found in both of these waves.

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b) Why are some people concerned about using microwaves?
c) Provide one use for microwaves.
d) Name two other electromagnetic waves that can be used for communicating.
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2. Wi-Fi is used by laptops as a wireless way to connect to the Internet. It uses microwaves that link to a router.
a) The microwaves have a wavelength of 12.5 cm and travel through the air at 300 000 000 m/s. What is the frequency of the microwaves which link the laptop to the router?
b) Wi-Fi is used in most schools. However, some people believe that it’s dangerous for children. Some scientists think further research is required. How could it be proved that there could be dangers?
c) Why do the scientists think further research is needed?

3. Edwin Hubble in 1929 first observed light from other galaxies is traveling away from Earth.
a) What is red-shift?
b) A group of scientists decide to observe red shift for themselves. They observe two galaxies: K and L. The light from galaxy K has a smaller red-shift then that coming from galaxy L. What does this tell the scientists about these two galaxies?

c) One galaxy, the Andromeda galaxy is moving towards the Earth rather than away from it. The light from this galaxy shows a blue-shift. When viewed from Earth, how do the frequency and wavelength from Andromeda seem to have changed?

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ANSWERS

1. a) Answers include:
– They travel at the same speed
– They can travel through a vacuum
– They transfer energy
– They can be reflected
– They can be refracted
– They can be absorbed
– They can be diffracted
-They can be transmitted
– They’re transverse waves
b) Due to the health risks.
c) Answers include:
– Microwaves
– Mobile phones
– Satellites
d) Infra red and Radio

2. a) 2400000000 hertz (Hz)
b) Conduct scientific research.
c) To discover if there’s a hazard or not.

3. a) The wavelength of light seems to increase.
b) Galaxy K is closer to the Earth than L and is moving away from Earth more slowly then galaxy L.
c) The wavelength is decreased and the frequency is increased.