darantjohnson
26.04.2020 •
Biology
One method used to measure water pollution by organic waste is to calculate the biological oxygen demand, BOD. This determines the rate at which oxygen is used by micro-organisms in the water.
To determine the BOD of water, a sample of water is taken from the sea or river and the concentration of oxygen is measured.
The sample is then placed in a tube with an airtight seal and kept at 20*C for five days. The concentration of oxygen is then measured again.
The fall in oxygen concentration is the BOD.
Suggest why the airtight seals are placed on the tubes.
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Ответ:
Long wavelength, low frequency waves, such as radio wave seas are thought to be harmless. They don’t carry much energy and are therefore considered safe by most people.
As the wavelength decreases and frequency increases, the energy increases - for example X-rays and gamma radiation. We know those are harmful to humans.
Explanation: