# Web-accessible remote laboratory (WARL)

Web-accessible remote laboratory (WARL). WARL extends access for high schools students to advanced laboratory infrastructure typically hosted by universities. The remote laboratory allows performing measurements without having physical access to the equipment, often too complicated or too expensive to be available in secondary schools. From a user perspective, WARL requires only access to the Internet – a user needs just a modern web browser, which is almost always already installed on a computer connected to the Internet. The main advantage of WARL is that a student is able to carry remotely physical experiments using real instruments, control measurement parameters and then analyse real data.

Our platform WARL is called also Internet Laboratory of Physics.

# Laboratory manual

Extensive laboratory manual is hosted here

# List of experiments

Aim of this exercise is to teach the student random fundamental properties of gamma radiation, and underlying statistical properties of nuclear and high energy physics.

This experiment has two modes:

• Background radiation measurement: in this mode students can measure background radiation in the room experiment is taking place. This informs students of the fact that: background radiation is omni present. Also this mode teaches students statistical properties of radiation --- as we present students with plot of current average cps as function of time --- this average fluctuates statistically.
• Material measurement: Where students see plot of impulses registered by Geiger-Muller counter as a function of thickness of material gamma radiation passes through, this follows exponential decay;

### Michelson

This experiment allows student to use Michelson interferometer for microwaves, this device was used by Michelson and Morley to disprove existence of luminiferous aether (a postulated medium in which light travels), and pave the way to special theory of relativity.3

In this experiment students are able to control Michelson morley experiment and observe light interfernence (which is one of the wave properties of light).

### Snellius

In this experimet students control laser pointer that shines beam on to glass/air barrier. Students can learn basic refraction law: Snells Law.

### Hall effect

The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current.

This effect is caused by magnetic field exerting force on electrons inside the conductor. This effect is used for:

• High-precision magnetic field sensors.
• Current sensors that can be placed outside the wire without any physical contact with the wire.
• As a propulsion system for space robotic space vehicles, as well as a position and orientation control engines for satellites.

In this experiment students can directly measure hall effect properties, that is:

• Hall voltage as function of magnetic field strength
• Hall voltage as a function of hall current

### Doppler effect

In the doppler effect experiment students can measure doppler effect, that is percieved difference in wavelength when wave source moves in relation to the detectore.

Doppler effect has many uses:

• High-bandwidth communication with satellite sources needs doppler compensation;
• To measure speed of objects using a doppler radar (both military uses as well as catching speeding drivers);
• Doppler effect is used to measure blood speed flow inside veins;
• Measuring relative motion between Earth and the stars. This has proven that universe is expanding.

In this experiment students controls speed of moving ultrasound source, and reads measured frequency.
This can be used to estimate speed of sound in air.

In this experiment student can measure radiation of a black body (black body is a theoretical fully opaque and not-reflective body that absorbs all radiation that shines on it. Good example of black body is sun, and good enough is a fiber inside turned on incandescent light bulb).

Due to thermidynamic laws black body also emits radiation, plancks law governs how much energy is emited for different frequencies in a function of temperature.

Plancks law can be applied to masuring temperature of objects that approximately can be treated as black-body:

• Corona of sun
• Distant stars and planets
• furnace temperature

Blackbody radiation also is not explainable by classical mechanics, and were explained by assuming quantum nature of light.

In this experiment student can directly measure radiation from a light bulb at different temperatures of the fiber.

### Photoelectric effect

Photoelectric effect occurs when electron are emitted from a material when light shines on them. To cause light emission length of light needs to be below certain threshold. This thresholding effect can not be explained using classical mechanics.

Photoelectric effect is used in photodiodes that e.g. count persons entering a place, it was used in early cameras (as a light sensor). Also photovoltanic panels use photovoltanic effect to produce electric power (photovoltanic effect is closely related to photoelectic effect).

In this experiment students can measure current through a photodiode as a function of voltage applied to it and wavelength of light that is shining on it.

### Geiger counter

Geiger-Muller counter is a basic radiation detection device used throught through the world, due to simple construction and low cost.

In this experiment students can measure number of impulses registered by the GM counter as they increase voltage on the Geiger-Muller tube. In practical applications voltage on GM tube is factory-set, and here we can teach students how this pre-set voltage is selected. GM counter exhibits very interesting nonlinear characteristics.

# How to use the Laboratory

Go to: http://silf.stem4youth.pl/