38-41;Elasticity/Travelling waves/Wavelength/Doppler Effect/

Question 1

elasticity

Answer 1

property of object that restores to its org dimensions after distorting froces are removed

EG spring/rubber band; when stretched will return to its og length = demonstrates elasticity

Question 2

hooke’s law

Answer 2

linear relationship, deformation of elastic solid proportional to deforming force

Question 3

periodic motion

Answer 3

motion which repeats itself at regular time intervals

characteristic of elastic objects moving under influence of Hooke’s forces

= when spring hung vertically w/ mass suspended = spring stretches until elastic restoring force is great enough to support weight

when mass pulled down and releases = oscillates up and down in simple harmonic motion = finally at rest until energy has been dissipated into U

Question 4

amplitude of motion

Answer 4

max distance moved from equil point

Question 5

resonant frequency

Answer 5

periodic motion occurring at one or more natural freq

determined by physical properties of system EG mass/lengt/stiffness

Question 6

travelling waves

Answer 6

any part of elastic object disturbed to propagate to all parts of object

matter w/ definite equil state has a tendency to periodic motion, in extended body = periodic motion takes form of travelling wave

EG waves in a pond

Question 7

transverse waves

Answer 7

particles of medium oscillate back and fourth perpendicular to direction of propagation of wave

EG waves in string, light/radio/x-ray waves

Question 8

longitudinal waves

Answer 8

periodic motion of particles parallel to propagation direction

EG sound waves

Question 9

speed of propagation

Answer 9

determined by the medium in which the wave is travelling, not freq/amplitude of wave

Question 10

wavelength

Answer 10

shortest repeat distance for periodic wave

distance btw crest/compressions of spring

Question 11

freq

Answer 11

no. of times a periodic function/vibration repeats in 1 sec

Question 12

wave properties of sound

Answer 12

sound= travelling pressure wave, can be propagated though a material medium but cannot travel through vacuum

audible sound = 20-20000Hz
Ultrasound = f>20000Hz
infrasonic f<20Hz

sound originates when elastic object vibrates back and fourth rapidly = sends audible freq thru medium in which it vibrates

EG tuning a fork

Question 13

wave properties of light

Answer 13

travelling wave consisting of propagating electric and magnetic fields

transverse wave v=2 x 10^8 m/s

infrared/uv = waves w/ freq below and above visible light

Question 14

energy in waves

Answer 14

all travelling waves carry certain amount of energy that travels in ordered motion until finally dissipated into disordered motion IE internal energy

Question 15

interference

Answer 15

addition of 2 or more waves that pass the same point in space

destructive Interference = waves from 2 diff sources meet w/ same amplitude = will cancel each other = leaves momentary flat spot

constructive interference = 2 wave crests coincide and add = produces larger crest

Question 16

standing wave

Answer 16

interference btw reflected waves so will vibrate up and down in fixed segments = natural/resonant freq

Question 17

doppler effect

Answer 17

EG when vehicle passes you, noticeable drop in pitch of sound of siren

Due to sound wave consisting of series of high and low pressure areas in air
v=345 m/s at T=20 C

Question 18

generalised doppler equation

Answer 18

used when source or observer may be moving w/ respect to the medium

Question 19

doppler shift

Answer 19

when sound source is stationary and observer is moving

DS of light freq = astronomers measure speed of recession of distant stars

DS of freq of microwave radiation = air traffic controllers measure speed of approaching aircraft

Question 20

ultrasound uses

Answer 20

SONAR/SOund Navigation And Ranging

use of US echo for:
- observing blood flow through major arteries
= US from source transducer produces DS that echoes off moving RBC into arteries = doppler probe can locates constrictions of vascular system = identifies increase of speed of blood flow

-detecting foetal heart tones
= US waves directed at body = reflections at interface between diff tissues/fluids produces change of speed of sound = speed of sound depends on density = outlines produced due to density changes