a proper real life phenomena related to atomic physics
Answers
Theoretical physics is the study of models of reality. Anything that happens can have a model built of it using the techniques of theoretical physics.
Experimental physics is the study of measurements of reality. Anything that happens can be measured using the techniques of experimental physics.
‘Branches’ of physics are something between an abstraction and a fiction. They are necessary in order to group the work into sensible groups, because nobody can know everything, but they aren’t real - I work in semiconductors, but I read books and papers about everything from soap to crystals for work purposes.
THAT SAID:
Mechanics, the study of moving and stationary objects, is fundamental to the engineering of nearly every sort of thing that humans build. In The Great British Bake-Off, there was an episode where the bakers built displays out of gingerbread. One of the bakers had done engineering at Cambridge. During the episode, as a throwaway comment, he mentioned that it didn’t matter what he was using to glue his display together with because the glue had no force on it. His knowledge of statics, which is a branch of mechanics, is what allowed him to calculate this and design a display that relied on the (fairly strong) compressive strength of gingerbread rather than the (fairly weak) tensile strength of royal icing.
A pendulum clock works because of the equivalence of gravitational and inertial mass, meaning that the period of the pendulum is independent of the mass of the pendulum bob. As I learned more physics, it seemed more and more miraculous that this works.
Still in mechanics, the conservation of angular momentum is behind the gyroscope effect that keeps a bicycle upright - and is the cause of the force that causes it to turn one way or the other if you lean it.
The atomic clocks in GPS satellites run veeeerrry sliiiiightly slower than the reference ones kept on the surface of the Earth. This is due to relativity - time dilation - and until it was accounted for it created a hard limit on the accuracy of GPS.
Light can be thought of as containing electric and magnetic fields, which we model with scientific theories collected and refined by Maxwell. These fields, Maxwell says, are directional. Light that has a specific direction to its fields is called polarised light, and you can make materials called polarisers that are nearly transparent to one direction and completely block the other direction. This science is fundamental to the LCD, the commonest sort of display screen on the planet.
The other part of your LCD phone screen is probably these days an LED. Inside an LED there is a material where charge is carried by electrons, and another material where it is carried by what’s called holes, basically bubbles where electrons are missing. When a hole meets an electron it releases much of the energy it has as light - so by putting electricity into this material you get light out. (This is the branch of physics I work in.)
Molecules in a substance vibrate, and bounce off one another, and exchange energy all the time. Unless there is an external influence guiding it, this exchange is fairly obviously random. Maths tells us that random actions on any system make it less ordered, not more ordered. So if two substances with different amounts of energy in their molecules are touching each other, then on average the system will work to make it less ordered, that is to equalise their temperature - the molecules with more energy have more to give away. The amount of energy in the molecules of a substance is more commonly called its temperature. So because of maths and the behaviour of randomness and no other influence or anything, heat flows from hot to cold. (This knowledge is either beautiful, in which case you should seriously think about studying physics, or boring, in which case you may go about your business :P )
Mixing a bunch of the previous branches together - electrons moving in a circle generate radio waves or - if you can get the circle small enough - microwaves. You can make electrons move in circles fairly easily with a combination of electricity and magnetism - and if you’re using electromagnets you can tune the size of the circle accurately so you can get the microwaves you want. Microwaves are interesting because they have the right wavelength to make the electrons in water vibrate, gaining heat. Thus, by a fairly direct route, we get the microwave oven.
Which leads us on to high energy physics and semiconductor physics. X-rays and other high energy radiation can knock electrons out of atoms - this is called ionisation. Those electrons can be picked up by a semiconductor-based detector, which works a great deal like an LCD screen in reverse: this can be used to take images that can see through normally opaque objects. Yes, medical / dental X-rays came originally out of the study of radioactive materials - though these days we generate X-rays using what’s basically a glorified microwave.