instruction:
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
question:
Waves contain?, Context: As an electro-magnetic wave travels through the different parts of the antenna system (radio, feed line, antenna, free space) it may encounter differences in impedance (E/H, V/I, etc.). At each interface, depending on the impedance match, some fraction of the wave's energy will reflect back to the source, forming a standing wave in the feed line. The ratio of maximum power to minimum power in the wave can be measured and is called the standing wave ratio (SWR). A SWR of 1:1 is ideal. A SWR of 1.5:1 is considered to be marginally acceptable in low power applications where power loss is more critical, although an SWR as high as 6:1 may still be usable with the right equipment. Minimizing impedance differences at each interface (impedance matching) will reduce SWR and maximize power transfer through each part of the antenna system.
answer:
power

question:
It became easier to move around in non-deep water thanks to what living entity?, Context: The tide-predicting machine invented by Sir William Thomson in 1872 was of great utility to navigation in shallow waters. It used a system of pulleys and wires to automatically calculate predicted tide levels for a set period at a particular location.
answer:
Sir William Thomson

question:
How does Atticus face the racism?, Context: The theme of racial injustice appears symbolically in the novel as well. For example, Atticus must shoot a rabid dog, even though it is not his job to do so. Carolyn Jones argues that the dog represents prejudice within the town of Maycomb, and Atticus, who waits on a deserted street to shoot the dog, must fight against the town's racism without help from other white citizens. He is also alone when he faces a group intending to lynch Tom Robinson and once more in the courthouse during Tom's trial. Lee even uses dreamlike imagery from the mad dog incident to describe some of the courtroom scenes. Jones writes, "[t]he real mad dog in Maycomb is the racism that denies the humanity of Tom Robinson .... When Atticus makes his summation to the jury, he literally bares himself to the jury's and the town's anger."
answer:
without help