AQA GCSE Electromagnetic Waves Interacting with Substances(Physics)
Electromagnetic Waves Interacting with Substances
When electromagnetic waves strike a substance, they can be reflected, refracted, absorbed or transmitted.
What happens will depend on:
1.The substance
2.Wavelength of the electromagnetic wave.
Reflection
Certain materials reflect EM waves instead of absorbing or transmitting them. The reflection can be specular (mirror-like) or diffuse (scattered), depending on the surface texture. Metals, for example, are good reflectors of visible and infrared radiation.
Below is reflection of visible light from a mirror as an example
Refraction
When an EM wave passes from one medium to another, its velocity changes, causing the wave to bend or refract. The degree of bending depends on the material and the wavelength of the light (e.g., A ray of light is refracted when it passes from air into glass at an angle other than 90 degrees.).
In the example below as the ray of light enters the glass block its velocity will decrease, so it refracts towards the normal line
Absorption & Transmission
When an electromagnetic wave strikes the surface of an object it is possible that the wave can be partially absorbed and partially transmitted as shown below.
The material will absorb some of the energy of the wave, so the amplitude of the wave decreases. As a result the transmitted wave has a lower amplitude. However, the material will gain energy, so its thermal energy store will increase.
It is also possible that the material could completely absorb all of the energy of the electromagnetic radiation and not transmitted wave occurs.
Example of absorption include greenhouse gases absorb infrared radiation, while pigments in paints absorb specific visible light wavelengths.
Practice Question
1.When an electromagnetic wave strikes a substance what can happen to the wave?
2.Define refraction.
3. Suggest why glass can cause significant refraction of visible light rays, but radio waves only show a small amount of refraction.
4. Describe an experiment to investigate the emission of infrared radiation from different surfaces
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Accordion Content
Accordion Content
Accordion Content