EM Waves & Atoms
- Atoms can interact with electromagnetic (EM) waves in one of two ways, they can be:
- Absorbed
- Emitted
- When an EM wave hits an atom, it can be absorbed by one of the electrons giving it energy
- This causes the electron to move up to a higher energy level
- If an electron moves down to a lower energy level it will emit an EM wave in the process
- In this way, atoms can absorb and emit electromagnetic waves over a wide range of frequencies
The electrons orbiting atoms can absorb and emit EM waves by moving between different energy levels
- The energies associated with electron transitions tend to be in the visible and ultraviolet range (and sometimes X-rays)
- Higher energies (ie. gamma rays) can only be achieved when EM waves interact with the nucleus
- The nucleus of an atom can absorb and emit EM waves in a similar way to electrons
From my experience of teaching 'EM waves and Atom's to GCSE students, they tended to find the topic a little dry. Some may have even uttered the word ‘boring’. I love electrons! These mysterious little particles are the reason I fell in love with Physics! So, I would accept the challenge to change my student’s minds.
Electrons are part of an atom and you are made of atoms, so you have billions of electrons that are a part of you. Electrons can get excited, and when they do, they can ‘jump’ to a higher energy level. If they get excited enough, they can leave the atom altogether. That fact right there is what Chemistry is all about, the ability of electrons to change energy levels and move to other atoms.
So, how do you excite an electron? One way is to get it to absorb an EM wave. I would get some tennis balls that represented UV rays. When I throw the tennis ball to a student, the student stands up. This represents the electron moving to a higher energy level. The electron has absorbed the UV ray and gained its energy. The student then throws the tennis ball back to me and sits down. The electron has emitted a UV ray, and so lost the energy it gained and has fallen back down to a lower energy level. This would often lead to a discussion about the mysterious behaviour of electrons, which allowed me to give the students a preview of what we study in A Level Physics, such as Young’s double slit experiment. Is an electron really a particle? Or is it a wave?
