what dictates the frequency of the waves?

what dictates the frequency of the waves?

The frequency of ocean waves depends on the wind speed, the time that the wind has been blowing and the length of the sea that it is been blowing over which is what we call the fetch. We actually prefer to talk about the period of waves, which is the inverse of frequency because people like to think about numbers greater than one rather than thinking about small decimals. If you started with the wind blowing over calm water, the waves start with small heights and short lengths but these steadily increase. In deep waters, the waves with the longer lengths travel more rapidly and the growth continues until the speed of the waves is about the same as the speed of the wind when it can’t put any more energy in. And we describe this as a fully-developed sea. There’s actually been a mixture of periods and people are quarrelling about how you define the period in the mixture of them. Real seas often have a spectrum with more than one peak, showing that the waves are coming from more than one place or maybe that the wind speed changed while they were growing. Periods in seconds of the same sort of order as wind speeds measured in meters per seconds, a bit more or a bit less depending on how you define your period. And most sea waves have periods in the range of 5 to 15 seconds with the longer ones coming when you had a really fast wind blowing for a long time over a long bit of sea.

Why is flu more prevalent in winter?

Why is flu more prevalent in winter?

we think flu spreads better in winter because of human behaviour because it does this reproducibly in every country in the world and in which it is winter time - it doesn’t mean it goes away completely in summer but it does come much more commonly in winter.

We think that’s because it spreads better in winter because of what humans do. We go indoors more in winter so there are more people together indoors with the windows closed. Also, unlike summer time, it’s less light and therefore there's less ultraviolet radiation to dry out the virus and kill it. So 'flu finds it easier to persist on surfaces spread by coughs and sneezes, and it hangs around for longer.

As a result you have a higher chance of passing it on so that’s what we think goes on. And then the big determinant, the disproportionate determinant, is the school year. The long summer school holiday powerfully knocks 'flu on the head because kids stop mixing and spreading the infection amongst themselves. What normally happens is that they become infected and then go home and give it to their parents and the parents then carry the infection to all of the other parts of the social and age strata, usually through their workplace.

Why does lemon make green tea go clear?

Why does lemon make green tea go clear?

There’s probably two reasons for this. The first one is that the lemon is acidic and so it’s affecting the pH of your tea and it may be that it’s causing changes in the chemicals that are in your tea and making them change to a different colour. So, like you can make indicator paper and change colour with different acids or bases and I think also, certainly down the south, we have a lot of limescale which is calcium carbonate in our water and it can make your tea cloudy. So, if you put in an acid, it will help to dissolve the calcium carbonate in it so it makes it go clearer.