Anderer Ressourcentyp

Siemens Stiftung

Optics - The physics of light

Information sheet:
Starting from the definition of light, light is described concisely in its various forms as a ray, as a wave, and as radiant energy.

Introduction to optics.

Information and ideas:
Intended as preliminary information for students as well as for teachers.

Anderer Ressourcentyp

Siemens Stiftung

A1 Electric current from solar cells (link list)

Link list:
Further information on the experiment "A1 Electric current from solar cells - We build a dye-sensitized solar cell".

The links can be used for preparing or for further study of experiments from Experimento | 10+.

Video

Siemens Stiftung

Subtractive color mixing

Video (00:12 minutes, without sound):
A student creates mixed colors and black by superimposing colored foils in cyan, yellow and magenta.



Primary colors are yellow, cyan and magenta. If you mix all three colors with full intensity and in the same proportions, you get black, i.e. no light is reflected.

Information and ideas:
Subtractive color mixing is used when working with colored substances and is therefore familiar to everyone from art lessons, for example from painting with water colors. The example shown can be easily replicated by students. If necessary, use cheap colored clear plastic folders instead of photo filter films.

Medientypen

Video

Lernalter

6-18

Schlüsselwörter

Color Light

Sprachen

Englisch

Anderer Ressourcentyp

Siemens Stiftung

Lens and imaging equation

Interactive schematic diagram:
The light rays emanating from the object must be collected through a lens to form the points of an image. The imaging equation describes the applicable laws.

The graphic can be labeled interactively, either individually or in full. Manual labeling on the interactive whiteboard is also possible.

Medientypen

Anderer Ressourcentyp

Lernalter

13-18

Schlüsselwörter

Light Optics

Sprachen

Englisch

Bild

Siemens Stiftung

Tree

Photo:
A group of trees in late summer. Photosynthesis only takes place in the green leaves.


Information and ideas:
An example of the conversion of radiant energy into chemical energy.

Bild

Siemens Stiftung

The Ear, Hearing and Hearing Impairment: Refraction

Graphic:
The wave front model of refraction on an interface makes it clear why the direction of the sound propagation changes.

When waves cross over from one medium to another, the speed at which the waves spread changes. Consequently, the wave normals of the incident and broken waves have different directions. With light waves, the change in the index of refraction at the boundary is the cause; with sound waves, it is the change in the density.
The graphic illustrates the case when the speed of propagation becomes slower at the transition from the first to the second medium: The wave is broken at the perpendicular of the boundary surface.
An explanation of this phenomenon is provided by the Huygens' Principle: Every point on a wave front is the starting point for a new wave, known as an "elementary wave". The enclosing end of the elementary wave creates the new wave front.

Information and ideas:
Refraction at boundaries also occurs with sound waves (for example, in the atmosphere at the transition from warm to cold layers of air).

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves

Bild

Siemens Stiftung

The Ear, Hearing and Hearing Impairment: Diffraction

Graphic:
Diffraction of waves on encountering an obstacle.

The graphic shows possible diffraction effects according to aperture and wave length.

Information and ideas:
Diffraction arises in sound waves as well, for example at corners of buildings.
Further information regarding this graphic is available as information sheet on the media portal of the Siemens Stiftung.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves

Bild

Siemens Stiftung

;: Color and voltage of LEDs

Photo:
The operating voltage of LEDs depends on the color. This is an indication of discrete energy levels and the photon character of light.


What color an LED emits depends on the energy level of the charge transition from the non-conduction band to the conduction band. Depending on the basic material (Si, GaAs, GaN etc.) and doping, as well as the internal resistance every LED has a typical operating voltage (voltage = potential = energy difference). Although this is modified by the design (internal resistance, etc.), in the final analysis it is determined by the discrete energy level of the charge transition between non-conduction and conduction band.

Information and ideas:
The abstract principle of the quantization of energy in the form of photons is demonstrated clearly in an extremely simple experiment with four LEDs and a power supply unit. Red LEDs light up at a voltage from about 1.5 volts, yellow from about 1.9 volts, green from about 2.3 volts and blue from about 3.3 volts.
Instructions for building a variable LED color mixer can be found in the experimentation instructions "Experiments - energy quantization with LEDs" on the media portal of the Siemens Stiftung.

Text

Siemens Stiftung

Data transmission with LEDs

Web resource:
Researchers at the Fraunhofer Heinrich Hertz Institute in Berlin and at Siemens AG have successfully achieved a data transmission rate of 500 megabits per second (Mbit/s) using a commercially available LED.


This article provides information on the advantages of data transmission with light compared to wireless transmission and shows possible applications.

Information and ideas:
This technology is also applied in the construction of LED miniprojectors that can be integrated into digital cameras or mobile phones. This technology would make it possible, for example, not only to take photos but also to immediately project them on a wall. A small blue laser diode is used for this.

Bild

Siemens Stiftung

Lens and imaging equation

Schematic diagram:
The light rays emanating from the object must be collected through a lens to form the points of an image. The imaging equation describes the applicable laws.

At least two of the following rays are needed to construct the image:
· Ray from the object parallel to the optical axis (parallel ray)
· Ray from the object through the focal point of the lens (focal ray)
· Ray from the object through the central point of the lens (central point ray).

The central point ray passes through the lens without changing direction. The parallel ray passes through the focal point on the other side of the lens, and the focal ray becomes the parallel ray.

Note: The imaging equation is also frequently known as the "lens equation."

Information and ideas:
What are lenses needed for?

Medientypen

Bild

Lernalter

13-18

Schlüsselwörter

Light Optics

Sprachen

Englisch