Elecromagnetic wave / EMR ( part 2 )

1. Light can affects the movement of electric charges,example, photoconductivity¹,photoresistivity², photovoltaic³effect,and photoelectochemical⁴ effect.

Note :

1.  Photoconductivity – is an  electrical phenomenon which,a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, infrared light, or gamma radiation

2. Photoresistivity –  a resistor whose resistance decreases with increasing incident light intensity. A photoresistor is made of a high resistance semiconductor. If light falling on the device and it is  high enough frequency, and photons absorbed by the semiconductor give an electrons enough energy to jump into the conduction band,thereby lowering resistance.

3. Photovoltaic - is the creation of voltage or a electric current in a material, upon its exposure to light. Though the photovoltaic effect is directly related to the photoelectric effect, they are different processes. In the photoelectric effect, electrons are ejected from a material's surface upon its exposure to EMR. The photovoltaic effect is different as the electrons are transferred between different bands ( example,from valence band to conduction band )  within the material, resulting in the build up of voltage between two electrodes

4. Photoelectrochemical cells – also known as PEC solar cells generate electrical energy from light, including visible light.

electromagnetic wave / EMR

Electromagnetic radiation / electromagnetic wave

1. Its often abbreviated as emr / electro – magnetic – radiation,and one form of energy.

2. Example of EMR are,visible light¹,infrared radiation²,ultraviolet radiation³,radio waves⁴,x-rays,and gamma rays (all can travel at the speed of  about 3.0 x 10⁸ ms ¯¹ ).

3. EMR has the component of electric and magnetic field which perpendicular to each other.

4. It exhibits wave-like behavior as travel through space.

5. Can travel through both,vacuum and medium of material.Most of the waves cannot travel through vacuum and need a medium for transmission.

6. Electromagnetic radiation carries energy and momentum that may be imparted to matter with which it interacts

 Revision :

1. Visible light is one of EMR,that visible to human eye.It has wavelength about 380 nm – 740 nm / 400-790 THz.( THz aka terahertz always refer to electromagnetic waves when they are propagating at frequency level).This is the range that human eye will respond.

Many of the species can see light out of visible spectrum,example,bee and birds and many other species can see the ultraviolet light,which help them to find a nectar in flower (Nectar is a sugar-rich liquid produced by plant ) .

Example of visible light, Lasers, sunlight, fire, LEDs, light bulbs

2.  Infrared radiation also called heat radiation and has a wavelength longer than that of visible light.The image as what we see by using infrared radiation,figure 2 :

 

3.  Ultraviolet light,is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm.It can be found in sunlight. Although ultraviolet radiation is invisible to the human eye, most people are aware of the effects of UV example, sunburn.

UV light is categorized as non ionizing radiation.Meaning, it does not carry enough energy per quantum ( the minimum amount of any physical entity  ) to ionize atoms or molecules—that is, to completely remove an electron from an atom or molecule.

Sun as see by using UV light,

 

4. Radio waves has a wavelengths longer than infrared light.