Answer:
The depth of focus achievable with those lenses is small.
Explanation:
A larger aperture makes it much harder to focus on more than one object. When using a telephoto lens (the ones the question is referring to), the depth of focus is very small. For example, using a telephoto lens to take a photo of a runner might get the runner in focus, but certainly not the track, or the audience behind them. If you look at photos, especially older photos, of Olympians in almost any sport you can see this.
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If each side is 0.1 feet extra,
The volume will be 5.1*2.1*1.1= about 11.781.
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Answer:
As the height increases the pressure must increase.
Explanation:
When we add masses to the fluid, the amount of fluid in the tank increases, therefore its height increases and the pressure is described by the expression
P = ρ g h
where rho is constant for a given fluid and h is the height measured from the surface of the fluid.
As the height increases the pressure must increase.
Answer:
Speed of light
Explanation:
The famous Einstein's equation is:

where
E is the energy
m is the mass
is the speed of light
In this equation, Einstein summarized the following fact: mass can be converted into energy, and the amount of energy released in such a process is given by the equation.
An example of application of this equation is the nuclear fusion process. In a nuclear fusion, two lighter nuclei combine into a heavier nucleus. However, the mass of the heavier nucleus is slightly less than the sum of the masses of the two original nuclei: some of the mass of the original nuclei has been converted into energy, accorging to the previous equation.
Answer:
The internet is most useful to them because they use it to communicate.
Explanation:
If I were to send a message to my brother in Florida, through the internet, while I'm in Pennsylvania he would get it in minutes. On the other hand if I were going to meet him and then explain what I wanted to tell him in person it would take a much longer time.