Spectrometer

Light is kind of electromagnetic wave. Visible light for example, this is an electromagnetic wave which has wavelength that can be sensed by human eye. Source of light may emit light not only one wavelength. White light consist many wavelength from 380 nm – 750 nm. The proof about this is when white light (such as sun light) is refracted by prism, we can see many color (from red to violet) as a result. Color of light depends on the wavelength, so we can conclude that sunlight consist many wavelength.

Spectrometer is an instrument which can be used for measure light properties. The variable can be measured by spectrometer usually is intensity. Electronic spectrometer consists of device which can convert from light to electricity, it is called CCD.

The steps inside electronic-spectrometer are started with light enter the spectrometer, then a device (Prism or grating) refracts the light based on its wavelength. For example white light will be refracted into all of visible light wavelength. These wavelengths will be converted into electric signal by CCD. This signal will be transmitted to PC to be processed. Finally we can see the spectrum of light on the PC’s monitor. Usually electronic spectrometer is completed with its software which can be used to measure in several units, such as Watt, Lumen, Lux, etc.

Spectrometer is used for many applications, Such as solution identification and LED Junction temperature Measurement.

Thermal Insulation

When we put hot water inside thermos, water will still hot although it has been several hours. This also happens when we put cold water inside thermos. After hours, water will still cold. How come?

Some may think how thermos knows that inside is hot or cold thus thermos keep the water hot and cold. The answer of this question is Thermal Insulation. As we know that heat is transferred spontaneously from higher temperature to lower temperature. But if between hot and cold temperature is blocked by thermal insulation, heat transfer will be minimized. Actually it is impossible to makes heat transfer rate is zero. It means that although we put thermal insulation between two temperatures, heat transfer still occurs, but very small. By this explanation, we can say that hot water inside thermos also becomes cold but it needs long time.

When hot water is put in room temperature, water will transfer heat to the surrounding whether by conduction, convection or radiation. But when hot water is inside thermos, heat transfer is minimized. Thermos wall is made by thermal insulation material which has very small coefficient conductivity. This cause heat transfer from water to surrounding is blocked. So the temperature of water will stay hot until long time (longer than we put without thermos).

It also happens when cold water is inside thermos. Heat transfer should be from outside thermos to inside thermos because temperature water inside thermos is colder than surrounding. But this heat transfer is minimized by thermal insulation material. Therefore temperature water inside thermos will be kept cold for long time.

Pascal Application

Car can be easily lifted by hydraulic lift in garage is the example application of Pascal law. Another example is disc brake. The principle of these things are Pascal Law, that the pressure between two surfaces are same, thus bigger surface will have bigger force.

Hydraulic lift (Halliday Resnick: Fundamental Of Physics)

As we can see at the picture, surface area A1 is smaller than A2. Based on Pascal law, pressure at A1 and A2 are same. Pressure is force divided by area, P=F/A, thus force needed to lift the car will be much smaller than the weight of car.
    

Small force F1 makes pressure at A1, this pressure is transmitted to A2. The pressure work at A2 makes force with upward direction. The force produced in A2 will be much bigger than force applied F1. This is why car whose weight is very heavy can be lifted easily.

The same principle is also used in brake system, in this case is disc brake system. When brake handle is pulled with certain force, it will transmit pressure to another surface at other edge, and makes force to clamp disk. This disc is attached to the wheel, since the rotation of disc is de-accelerated thus the speed of vehicle also becomes slower.

Laser Based Manufacturing

The application of laser has been applied in many technologies. One of them is Laser based manufacturing. This technology is combined laser and photopolymer phenomena. Photopolymer is the phenomenon that polymerization of material by energy photon. Photopolymer material such as resin is liquid. If this liquid is shot by photon energy with certain wavelength, the phase will be solid because of the polymerization. Laser is narrow beam of light with very high energy. By controlling the beam of laser to the photopolymer material, an object can created.

The selection of laser type and photopolymer material is very important. Laser can be classified by its power and wavelength. Resin also can be selected based on properties. They have to be matched each other. If they are not match, failure will occurs. For example, the power of laser is too high, it will burn the resin. If wavelength of laser is not matched with resin’s properties, photopolymer phenomenon does not occur.

Controlling laser beam can be done by XY Scanner. This equipment can be programmed to drive laser beam. Inside XY scanner, there are mirror which has function to reflect the laser beam. By driving mirror movement, laser beam can be controlled.

This technology can be applied with another technology such as 3D camera. By taking 3D picture then process the data from picture to coordinates, it can be an input for XY scanner, thus laser beam can create the object which has the same with object taken by 3D camera. This kind of concept may be applied for construction of the skull of human. Before doctor do a surgery, this replica of skull can be used for practice.