With a little bit of trig, we get the following expression.Īlternatives for Your House: Outdoor Lasers and LED Projections Light will constructively interfere when this path length is an integer multiple of the wavelength of light. By changing the angle that light comes out of the slits, you would get different path length differences. This light can be represented as different light rays. If we have light going through a bunch of openings, then this light will diffract in such a way that it will expand as it goes out of the slit. This is usually accomplished by using a series of super tiny lines on a glass plate-called a diffraction grating. Let me just consider the method of using multiple openings. There are all sorts of ways to get light to create an interference pattern when it shines through an opening. If both the waves are in phase such that their peaks are lined up, then the amplitudes of these waves will add together and produce a wave with twice the amplitude. First, there is constructive interference. There are two extremes of what can happen.
Since red light has a wavelength of 650 nanometers, you need really small openings.īut what happens when two waves from different sources are at the same place and the same time? This is what we call interference. You only get noticeable effects when the size of the opening is around the same size as wavelength. It turns out that the amount of bending for waves that travel through an opening depends on both the size of the opening and the wavelength of the wave. We call this diffraction.īut if waves bend through openings, wouldn't that mean you could see around a corner of a doorway? In theory, yes. It turns out that when a wave (like light) passes through an opening, it sort of re-radiates. So, how do you take one laser and with it make many spots on your house? The answer is a diffraction grating-which is essentially a device with many super tiny lines on it.
Yes, these are just approximately true-but let's just work with this for now. The laser light is collimated-such that it mostly just goes in one direction with very little beam spreading. This means that all the light produced is in phase such that you could think of it as just one wave (with one wavelength). So, a red laser creates light with a wavelength of something like 650 nm. They mostly just produce one color of light (and thus one wavelength). I'm not going to talk about lasers today (but I will in the future) except to say the following: The first element of this device is the laser. It's not quite as bright as your traditional lights, but it's so simple to set up.
When Christmas time is over, just pick up the laser out of the yard. These spots then look like little bitty lights.
The basic idea is to stick a small device in your yard that shoots lasers at your house to make some spots. Yes, you can now add Christmas lights to the outside of your house with lasers. This year, we are using something different-lasers. All you need to do is stake it into the ground, turn it on at the wall and you 've got sparkles in seconds.Ĭhristmas lights on the outside of your house might look awesome, but they really aren't that much fun to hang up. No ladders, no time-consuming decorating - a laser light projector is a godsend if you want hassle-free decor.