Answer:
The convex lens is shaped so that all light rays that enter it parallel to its axis cross one another at a single point on the opposite side of the lens.
Explanation:
By tightening a string you are actually putting more stress on the string you are giving it a new frequency that isn't natural.
Hope this helps
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Answer:
Explanation: y’all taking the same test as me hahahahah I got the answers but I can’t attach the picture here so hit me up on snap daniela_0789
Mainly because of the higher energy of blue light than red light.
In fact, light is made of photons, each one carrying an energy equal to

where h is the Planck constant while f is the frequency of the light.
The frequency of red light is approximately 450 THz, while the frequency of blue light is about 650 Hz. Higher frequency means higher energy, so blue light is more energetic than red light and therefore it can cause more damages than red light.
Answer:

Explanation:
For sound waves we have v=d/t where v is the speed of sound and d the distance between the astronauts, while for electromagnetic waves we have c=D/t where c is the speed of light and D the distance between the spaceship and Earth. <em>We have written both times as the same</em> because is what is imposed by the problem, so we have t=d/v=D/c, which means:

And for our values:
