Test #2 April 1 st Energy Light and Electromagnetism Electromagnetic Radiation

Chapter 6 Work Formula to find the work done on or by an object is W = F x d Has units of Joules (J) 1J = 1 N m

Chapter 6 Energy –Is the ability to do work –Has units of Joules (J) Work-Energy Principle –Work is an energy transfer. –Work tends to reduce the energy of the system doing work or increases the energy of the system on which work is being done on.

Chapter 6 Law of Conservation of Energy –The total energy of a system before a reaction or process takes place is equal to the energy after the reaction or process takes place. –Can be symbolically represented by the formual E before = E after

Chapter 6 Types of Energy –Potential energy (PE) Book calls it gravitational energy PE = m x g x h The weight is given by m x g and is a force The height is given by h –Kinetic Energy (KE) KE = 1/2 m s 2 The m stands for mass

Chapter 6 Power –Defined as how quickly work can be done –Power = work done / time to do the work –Has units of Watts (W) –1 W = 1 J / s –1 kW = 1000 W –1 MW = 1 million (1x10 6 ) W

Chapter 8 Wave –Is defined as a disturbance that travels through a medium in such a way that energy travels through the medium but mass does not. –Has the following properties Frequency (f) is the number of vibrations of any particular point on the medium per second. –Has units of Hertz (Hz) –1 Hz = 1 / s

Chapter 8 Wave properties cont’d –Wavelength ( ) and Amplitude (A) Wavelength has units of meters (m) Wave speed is the speed at which the waves moves through the medium –Calculate wave speed (s) by using the formula s = f x

Chapter 8 Interference –A behavior unique to waves –Two types: Constructive and Destructive interference Constructive Interference –When two or more waves interfere with one another and combine together to make a new wave. Destructive Interference –When two or more waves interfere with one another and cancel each other out

Chapter 8 Young’s Double Slit Experiment –Interference of light coming from two slits was observed on a screen, demonstrating that light is a wave. Magnetic Force Law –Charged objects that are moving exert and feel a magnetic force beyond the electric force that exists when they are at rest. –Note: Magnetic forces are caused by the motion of charged particles.

Chapter 8 Electric Force Law F electric = k x (q 1 x q 2 ) / r 2 –k = 8.99 x 10 9 N m 2 / C 2 –q1 and q2 are the charges of the objects –d is the distance between the objects –If F is negative, the force is attractive –If F is positive, the force is repulsive

Chapter 9 Force Fields –The effect that a source of force has on the surrounding space. –This field can exist even if there is no material present. –Types of fields Gravitational Electric Magnetic

Chapter 9 Electric Field –Surrounds every charged object –Exists even if there are no charges present –What does the electric field look like for positive and negatively charged objects?

Chapter 9 Magnetic Fields –Surrounds a bar magnet and is caused by small electric currents in the material –What does the magnet field of a bar magnet look like?

Chapter 9 Electromagnetic Wave Theory of Light –Every vibrating or moving charged object creates a disturbance in it own electromagnetic field, which spreads through the field at 300,000 km/s. –Light is just such an electromagnetic wave

Chapter 9 Electromagnetic Spectrum –Electromagnetic waves occur over a wide range of frequency and all waves travel at the speed of light. –Energy of an electromagnetic wave is proportional to the frequency and proportional to 1 / wavelength.

Chapter 9 Electromagnetic Spectrum cont’d Electronic waves –Created by electronic circuits –Wavelengths are on the order of the size of the Earth all the way down to 1 mm. –Examples of electronic waves AM & FM radio waves, radar antenna, and power lines

Chapter 9 Infrared radiation –Caused by the thermal motion of atoms and molecules –Wavelength is on the order of 1 mm all the way down to 1/1000 mm. Visible radiation –Created by electrons moving within individual atoms –wavelengths range from x to 0.75 m x m

Chapter 9 Ultraviolet radiation –Created by electrons moving within individual atoms –UV radiation is readily absorbed by living things and can cause cancer.

Chapter 9 X-ray radiaiton –Created by machines and objects in space –Deeply penetrating and used to view the inside of the body without surgery and to treat certain forms of cancer. –Is one type of ionizing radiation

Chapter 9 Gamma radiation –Created by nuclear reactions and by radioactive materials –Is another type of ionizing radiation –Gamma radiation penetrates deeper into matter than x-rays. –Is also used to view the inside of the body without surgery.