Laser Pointer

Laser Pointer
Military-Grade Laser Pointer Blinds People 4km Away
The military have their own version of the old green laser pointer prank, one that can blind people 4km away (even if, at that distance, the blinding is temporary). They use it to hail and warn enemies trying to advance. (more…)
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How far does the laser from a laser pointer go?

If there were people on the moon for example, could they see my laser pointer if I somehow managed to aim it on the surface close to where they were standing?

And light is just made up of photons, so could one actually count the # of photons in a beam of light? I mean theoretically, are photons quantifiable?

People on the Moon would probably not be able to see your pointer. The beam from even the best lasers diverge somewhat so by the time light from a pointer reaches the distance of the Moon the intensity would be too low to be detected by eye. I'm sure there are some instruments that would be able to detect the light however.

I suppose you could count the # of photons in a beam of light. Some astronomical instruments detect only a very few photons from far away objects. Since the energy of a photon is h x f where h is Plank's constant and f is the frequency and since lasers are nearly monochromatic--one frequency--we could measure the intensity of the laser and divide by the energy of each photon and 'calculate' the # of photons.

Your Computer System

Your computer is a set of tools and you need all those tools to function effectively. It contains two major set of tools: software and hardware. Learning the hardware components of your computer system is important specially when getting started. Let's find out what they are.

Input Devices

An input device captures information and translates it into a form that can be processed and used by other parts of your computer. Input devices include a mouse, keyboard, trackball, touchpad, scanner, digital camera, digital video camera, and many others. These devices essentially help you enter information into your computer system so you can use and manipulate it. Desktop Computers always come with a mouse. On notebook computers, you'll also find another input device called a touchpad. A touchpad is a touch sensitive input device on which you move or slide your finger to cause your screen pointer to move accordingly. These are now the most common pointing input devices on notebook computers.

As you use your computer system, you're certainly not limited to capturing information that exists in a text or numeric form. You can also capture audio - using microphone, images, and video. A digital camera is an input device that helps you capture live photos and pictures and transfer them directly to your computer. A digital video camera is an input device that helps you capture live video and transfer them directly to your computer. With these two devices, you can easily capture photos and video and add them to your Web page.

Output Devices

An output device takes information within your computer and presents it to you in a form that you can understand. The most common output devices are monitors, printers, and speakers. As you might well guess, speakers are output devices that allow you to hear information.

Many of today's computer applications are multimedia-based. A multimedia is a presentation of information that can include sound, text, graphics, video, and animation and over which you have some sort of control. Monitors on the other hand, are output devices that display information to you on a screen. When you buy a monitor, you need to consider screen size, resolution, and dot pitch. Screen size defines the viewable area of the screen and is measured from one corner to the opposite corner. Most people prefer bigger screen sizes, but bigger screens also cost more money.

A printer is an output device that creates a hard copy or paper version of the information you want to see. Today's personal computer printers include inkjet and laser printers. You still might find some dot matrix printers in use, but they are quickly fading away. For both inkjets and lasers, the resolution of printer is the number of dots per inch (dpi) it produces, which is the same principle as the resolution in monitors. The more dots, the better the image, and, usually the more costly the printer.

In general, if you need color, you should probably buy an inkjet printer as opposed to a color laser printer. Color inkjet printers sell for as little as $100. However, if you want extremely high quality black-and-white paper prints, you should probably consider buying a laser printer.

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