It turns out physics is awesome.
Not that I didn’t know that, but in the last few weeks of labs I got to prove that to myself by playing around in a dark room saying “OOH! Look at that!” as we made holograms. Appreciating the beauty of nature can certainly be very satisfying, but little quite beats the instant gratification of seeing the etherial image of one’s wristwatch floating in mid air behind a transparent sheet of photographic film.
To make a hologram:
1. Go into a very dark room.
2. Switch on LASERs with a key (whilst pretending to be a bond villain).
3. Wear big green goggles to keep the LASER light out of your eyes (particularly when sitting – the plonker that designed the dark room thought it would be a great idea to have a desk that puts a seated person’s eyes exactly at LASER beam level).
4. Shout at your mates when they accidentally reflect LASER beams around the room.
5. Be thankful when the demonstrator (the person who assesses you, answers questions and is meant to know how how the experiment works) reveals the LASER has been downgraded making it unlikely to cause serious eye damage.
6. Spend lots of time working out how holograms work (Interested physicists: it’s to do with creating an interference pattern on the film that records the phase of the light from the object being imaged).
7. Use your awesome physics skills (or follow the instructions in the lab script) to arrange lenses, beam splitters, mirrors, and the thing you’re making a hologram of. Do this with the aim of getting a hologram at the place you’re going to put photographic film.
8. Block the LASER beam, put expensive special transparent photographic film in its holder then unblock the laser beam for 3-5 seconds.
9. Develop your film (whilst pretending to be an old school photographer)
10. Put your film back in the laser beam and… “WOW I CAN SEE MY WATCH! YOU CAN TELL WHAT MAKE IT IS AND EVERYTHING.” (or more commonly, “Oh, we’ve overdeveloped/underexposed the film.”)
11. Feel awesome.
12. Repeat steps 1-11 using a variety of shiny objects (coins, keys etc.)
The holograms are very difficult to take photos of, below is a video I made on my phone which gives you some idea of what they look like. With the naked eye, the detail is much more pronounced than shown in the video.
We also made some white light holograms of coins. These are like the holograms you get on tickets and bank cards. Unfortunately these seem to be almost impossible to take a photo of, but if you know me then I’ll gladly show you one. Instead, here’s a picture of the watch in the above video:
If you don’t know me then get a piece of transparent plastic and imagine seeing the green image of a coin floating behind it. If you turn the hologram over, you get the strange effect of the things that were sticking out looking like they stick in, as though it’s the imprint of the object in something like a piece of blu-tac. It’s very odd.
All this ignores all the time spent sitting in a dark room trying to understand the theory of how holograms work, writing in the lab book, and the 2 weeks previously spent trying to get a temperamental inteferometry experiment to work… but still, wow! Holograms!
So yes, physics is awesome.