Exam 2 (6,7,8)

Chapter 7

• Longitudinal - particle motion & wave velocity are parallel to each other

  • Sound is longitudinal

• Transverse - particle motion is perpendicular to the direction of the wave velocity

  • Ex: light

Wave motion: waves transfer energy and generally not matter through

Calculate wavelength * frequency from wave speed  - frequency x wavelength

Period - 1/frequency - know order, radio wave huge lengths small frequency, gamma waves, small wave length, huge frequency

Sound Waves - the propagation of longitudinal waves through matter (solid, liquid, gas)

• longitudinal - far away, compression - close together

Sound spectrum - has relatively few frequencies

• Divided into 3 frequency regions:

  • Infrasonic, f<20 Hz (20 or below)

  • Audible, 20 Hz < f < 20 kHz (20 Hz to 20 kHz)

  • Ultrasonic f > 20 kHz

Sound intensity - decibel scale, what measuring the rate of energy transfer through a given area

Doppler effect - objecting moving toward/away from us, change in frequency resulting from the relative motion

Standing waves - “stationary” waveform arising from interference of waves traveling in opposite directions

Resonance - wave effect that occurs when an object has a natural frequency that corresponds to an external frequency

Chapter 7

Reflection - The change in direction of a wave when it strikes & rebounds from a surface or boundary between two media

• Thought as light “bouncing off” a surface

Law of reflection - the angle of reflection 0r, is equal to angle of incident

Ray diagram - a straight line that represents the wave

Refraction - light hits surface, then bends

Index of refraction - speed of light in vacuum/ speed of light in medium

Internal reflection (critical angle) - light coming out of water, bends it, angle bends so much parallel on water

Dispersion - white light, hits prisms, shows all colors, bending

Spherical mirrors (terms used) - small, flat specular - vertex, primary axis?

Concave, convex mirrors (definitions, ray diagrams - image: dotted line, object: bold, image characteristics - real? Virtual image ?

Lens (types, ray diagrams) - image: opposite - real image

Vision defects (what lens would be used) - concave, convex (diverging lens)

Polarization - light coming at you all different directions, put slits up only letting certain light thru

Diffraction - bigger wave length, smaller object, bigger refract (curve), smaller, smaller refract

Interference -when 2 or more waves meet 

Chapter 8

Electric force - retractive or repulsive force, 2 pos & 2 pos get away, opposites attract - hold atoms & molecules together

Law of charges - like charges repel, unlike charges attract

Coulomb’s Law - Charge on single electron (-) proton (+)

Current (types, calculating) -  time rate of flow of electric charge 

• How fast electrons are moving down the line

  • I = charge/time = q/t

    • I = charge current (amperes)

    • Q = electric charge flowing past a point (coulombs)

    • T = time for charge to pass point

Conductors: materials in which an electric charge flows readily (most metals, due to outer most layer, loosely bound electrons

 insulators: matters that do NOT conduct electricity very well - due to very tight electron bonding

• Ex - wood, plastic, glass

Voltage - push in order to get current to go (force)

Ohm’s Law - V (voltage in volts) I (current in amperes) R = (resistance in ohms)

• 1 ohm = 1 volt/1 ampere

Electrical Circuit (open/closed, series/parallel) - electrons flow from negative terminal -> positive terminal (provided by chemical energy of the battery)

• Open switch: not complete circuit, no flow of current (electrons)

• Closed switch: a complete circuit & flow of current (electrons) exists

Electrical power -

• P = W/t (Power = work/time)

• V = W/q (Voltage = work/ charge)

  • Rearrange V=w/q -> W = qV

Magnetism - Electromagnetic waves consist of both vibrating electric & magnetic fields

• Bar magnet - 2 regions, North poles and South poles

• magnetic materials - ferromagnetic vs non ferromagnetic)

• Source of magnetism: moving and spinning electrons

  • Current open -> deflection of compass needle

  • Current closed -> no deflection of needle

Curie Temperature - temp of where magnetic materials STOP being magnetic

Magnetic Declination - geographical north (true) vs magnetic

Electromagnetism - interaction of electrical & magnetic effects

• Stronger current -> stronger magnet

Motors and generators - electric motor: device that converts electrical into mechanical work

Electrical transformers (types, voltage change) - step up or step down the voltage of electric transmissions

• 2 coils wire wrapped around iron core