The study of optics and waves is focused on how electromagentic radiation interacts with other objects and itself. While the term “electromagnetic radiation” is most often used in science fiction, it describes everyday phenomena such as light, x-ray, radio, microwave, infrared, and ultraviolet. All of these different types of energy are simply waves; oscillating patterns of electrical and magnetic fields which create a wave pattern. Whereas electromagnetic radiation is used in diverse applications, from heating food to viewing bone density, all types can be described with the same equations and the same physics.
The properties of electromagnetic radiation arise from differently sized wavelengths. For instance, the length of the wave roughly corresponds to objects it can interact with. Among the electromagnetic waves, radio waves are the longest, measuring in at one meter. Because of this, radio waves are used by radar systems to detect large objects such as airplanes or clouds while ignoring small objects such as birds. Meanwhile, light waves, which are 10,000,000 times smaller than radio waves, will interact with large objects all the way down to bacteria. At the shortest end of the spectrum are the gamma waves – these are so small and so high energy that they can break apart the fundamental pieces of matter.
So why do we see with visible light and cook with microwaves? What do the terms ‘seeing’ and ‘interacting’ mean when it comes to waves? By analogy, the waves of electromagnetic radiation are a bit like waves in the ocean. Picture an aircraft carrier – when it bobs in the water, it will create waves that are very far apart. Meanwhile, a seagull sitting in the water will make many small waves very close together. If you send many waves close together at an aircraft carrier, it will not start to rock whereas the same waves sent at a seagull will make it start to bob.
Electromagnetic radiation works in a surprisingly similar way. For example, infrared waves share approximately the same ‘energy’ as molecular vibrations. Molecular vibrations are responsible for heat, therefore, shining infrared waves on an object will cause it to heat up. Conversely, hot, vibrating molecules will send off infrared waves. This allows night vision goggles to visualize hot objects. Light waves carry the same ‘energy’ as pigments, and gamma waves the same ‘energy’ as atoms. For the same reason, ultraviolet waves give us a sunburn while innumerable radio waves can pass right through our bodies everyday without causing harm.
Beyond interaction, it is also very important to be able to ‘see’ electromagnetic radiation – this requires optics. Optics are used to focus larger electromagnetic waves such as light or radio waves. The ability of optics to ‘see’ things stops at the subcellular level. Once scientists want to visualize molecules, they need to step down to the shorter x-rays.
The use of x-rays to view objects on an atomic scale presents numerous problems. First and foremost, since x-rays are as small as atoms, no lens made out of normal matter can be used to focus x-rays. If one could be made, the inventor would win a Nobel prize instantly. Rather, advanced computational techniques must be used to calculate the structure of something through x-ray diffraction patterns. This field is known as x-ray crystallography.
Have more questions? This subject is an entire scientific field unto itself whose mysteries are still unfolding everyday.