1.
Given frequency, however, we can take the reciprocal to get the period. Hence a low frequency requires a long period.
2.
Stellar aberration (aberration of starlight) is a tiny annual shift in the apparent positions of stars, caused by Earth's orbital motion around the Sun. It was discovered in 1729. If rain is falling straight downward on a windless day, and then you start to run around a circular track, the rain will always seem to be slanting towards you: first from the north (when you are running northward), then from the east, then south, etc. So it is with starlight: The star seems to be shifted a bit north from its true position, then east, etc., repeating this cycle each year. In short, it seems to move in a tiny circle (actually a tiny ellipse) rather than always being in exactly the same position; the shifts are far too small to notice with the naked eye but can be observed via careful telescope measurements.
This is relevant because it contradicts the "ether drag" hypothesis. If all the air within, say, twenty feet of you followed you around the track as you ran, the rain would always reach you traveling straight downward, no matter how fast you ran or in what direction. So aberration showed that Earth doesn't have a large blob of ether that follows it around the Sun.
Note that stellar aberration does not demonstrate that there's no ether: It only demonstrates that Earth isn't dragging any ether along with it as it orbits the Sun. This is why physicists expected to be able to detect an ether wind "blowing" past Earth as it orbits.
3.
All but the fourth choice are correct. Any kind of light -- whether or not humans can see it -- is an electromagnetic wave. Ordered from low frequency to high, we have radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays. Equivalently, that list is ordered from long wavelength to short wavelength.
4.
Air molecules simply move back and forth when I speak; I don't produce a "wind." What's carried from me to you at wave speed v is energy. This is vitally important to understand: small back-and-forth motions of the medium produce a steady transport of energy.
5.
The equation involved is v = λ f. We know that v = 330 m/s, and we can compute that the frequency is the reciprocal of the period (i.e., 440 Hz, or 440 s-1 ). Dividing one by the other, we get 0.75 m as our wavelength.
By the way, this concert hall is having trouble with the heating system. The speed of sound in air depends on the air temperature, and the room evidently is at about 0°C.
6.
Maxwell's equations were solved to show that an electromagnetic wave can exist and that such a wave travels at the speed of light, c = 3 x 108 m/s. But this is the speed relative to what??? The equations don't say. So physicists hypothesized that space is pervaded by a very tenuous material called the luminiferous ether, and light was assumed to travel at speed c relative to this ether. Earth was thought to travel through this ether as it orbits the Sun, so that the speed of light relative to Earth would depend on whether a light beam was traveling with or against Earth's orbital motion; this is what motivated the Michelson-Morley experiment. Light does not travel at speed c relative to the light source, because this is how particles (projectiles) would behave, and light was known to be a wave rather than a particle. And of course the third choice seems to make no sense at all -- although it eventually turned out to be the right choice.
7.
We "add" waves when two wave sources are influencing the same medium; this is called interference. (You'll see a lot of this phenomenon this semester!) The result of wave interference depends on whether the two individual waves are "in synch" or "out of synch" with each other at a given place. (The technical terms are "in phase" vs. "out of phase.")
When crest combines with crest and trough with trough, we get a very large amplitude wave as our "sum": constructive interference. But if crests and troughs cancel each other, we instead get a very small amplitude sum: destructive interference. In fact, a whole range of possibilities between these two extremes exists, but we generally won't worry about that.
8.
Imagine that I'm driving at 10 m/s in a convertible with the top down, and that I throw a ball to Alice, who is standing on the side of the road ahead of me. If the ball's speed in my reference frame is 6 m/s then Alice measures the speed to be 16 m/s. Next, ignoring the danger, I turn around in the driver's seat and throw a ball at 6 m/s to Bob, who is behind me on the side of the road. In Bob's reference frame, the ball's speed is 4 m/s -- and it is moving forward, not backwards. These two results are just common sense for the motion of particles, for the motion of material projectiles.
Light doesn't seem to work that way. If it did, we'd see the light from an orbiting pair of stars traveling to Earth at two different speeds, faster for the star moving towards us at any given moment, slower for the star moving away. This would mean that the light from the first star would reach us sooner than the light from the second star. Put another way, a photograph taken with a telescope would show the positions of the two stars at two different times. Imagine that I take a double-exposure photo, showing you crossing the street at 1:00 p.m. and a car driving along the same street at 1:02 p.m.. My photo would look as if you were being run over by the car: a distorted view of reality. So it is that the two stars would seem to orbit each other in a strange, distorted way.
But in reality, double-star systems are observed to orbit each other just as we'd expect from Newton's laws of motion and his law of gravitation, not in a strange, distorted way. Thus we conclude that starlight travels to us at the same speed from both stars, regardless of which one is moving towards or away from us. This is how waves behave, not particles, so this is another piece of evidence that light is a wave.
9.
Any wave can show interference -- it's the wave phenomenon par excellence. In fact, by the end of the course we'll use interference to show that electrons, atoms, and bowling balls are waves! But let's not get ahead of ourselves....
10.
The second choice is correct: This is the phenomenon of electromagnetic induction. It doesn't matter whether the magnetic field is large or small (or if it points this way or that way); what matters is how rapidly the field's strength or direction changes.