WHAT IS A SOLAR CELL?
Devices that convert solar energy to electric energy.
WHAT IS PHOTO ELECTRIC EFFECT?
The photoelectric effect is a phenomenon in which electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light
Absorption and generation of exciton
Dissociation and
The most common form of solar cells are based on the photovoltaic (PV) effect
Two layer semi-conductor device produces a photovoltage or potential difference between the layers
No fuel cost or fuel supply problem
No pollution
High reliability
Small amount of power required
Depend on place and climate
Large scale:
Ocean navigation aid
Telecommunication system
Remote moni
effects are showing. The earth is warming up and climates are changing. There are parts in the world were there be more rain and sunshine and others parts will be come dryer then they already are. Another negative effect is that the ozone layer is getting thinner which also leads to a warming up of the earth. These two effects compliment each other and make it even more crucial to make another st
석유, 석탄, 천연가스 등의 화석에너지 자원들은 고갈되고 있고, 시대가 지나면서 에너지 문제의 중요성은 더욱 증가되어 에너지 안보 문제가 심각하다. 우리나라는 2009년도 기준 에너지 해외 의존도가 약 96.2%로 세계 에너지 시장의 변화에 취약한 구조를 가지고 있다. 특히 중동 지역의 의존도가 2008년
What is “Greenhouse Effect”?
is the warming that happens when certain gases in Earth's atmosphere trap heat.
A multilateral agreement
based on absolute
mandatory caps for
Annex 1 countries.
joint implementation
clean development mechanism
Emission Trading
1. What is Ionizing Radiation?
Ionizing Radiation
: has sufficient energy to remove an electron from an atom
Ex. α-particle, β-particle,
X-ray, γ-ray
Free Radical :
molecule containing unpaired electrons
2. Effects of Ionizing Radiation
Radiation causes ionization of atoms which are forming cells.
→ Tissues
→ Organs
→ The whole body
Cellular Damag
radiated , rad (1 Gy = 100 rads).
International health and safety authorities have endorsed the safety of irradiation for all foods up to a dose level of 10,000 Gy (10 kGy).
1895 Discovery of X-rays
1986 Discovery of natural radioctivity
1904 Describing the bactericide effects (MIT)
1918 US-Patent to use X-rays for the preservation of food
1921 Describing the elimination of
radiation has demonstrated practical benefits when integrated within an established system for the safe handling and distribution of food. In addition, with increasingly restricted regulations or complete prohibition on the use of a number of chemical fumigants for insect and microbial control in food, irradiation is an effective alternative to protect food against insect damage and as a quaranti