hl definitions

Question 1

angular frequency (ω)

Answer 1

the angular speed that an object undergoing uniform circular motion would have were it to match an object undergoing simple harmonic motion

Question 2

critical damping

Answer 2

damping where the simple harmonic motion stops the first time the object passes through the equilibrium position

Question 3

damping

Answer 3

the removal of energy from an object undergoing simple harmonic motion by a force opposing the motion

Question 4

diffraction grating

Answer 4

a screen that has hundreds of slits per mm through which light can pass

Question 5

Doppler effect

Answer 5

the change in frequency of a wave as a result of movement of the source or the observer

Question 6

modulation

Answer 6

the reshaping of a double slit interference pattern by single slit diffraction

Question 7

Rayleigh criterion

Answer 7

occurs when the maximum of one diffraction pattern is over the first minimum of the other

Question 8

resolution

Answer 8

the ability to detect the two light sources as seperate

Question 9

resolvance (R)

Answer 9

(of a diffraction grating) - the ratio between the wavelength being investigated (λ) and the smallest possible resolvable wavelength difference (∆λ)

Question 10

electric field

Answer 10

a region of space where an object experiences a force because of its charge

Question 11

electric field strength (E)

Answer 11

the force per unit charge experienced by a small positive test charge placed in the field

Question 12

electric potential (Ve)

Answer 12

work done per unit charge in bringing a small positive test charge from infinity to that point

Question 13

escape speed (Vesc)

Answer 13

the speed a body needs to escape the gravitational attraction of a planet (i.e. to reach an infinite distance away) from the surface of the planet

Question 14

gravitational field

Answer 14

a region of space where an object experiences a force because of its mass

Question 15

gravitational field strength (g)

Answer 15

the force per unit mass experienced by a small point test mass placed in the field

Question 16

gravitational potential energy (Ep)

Answer 16

the work done in moving a mass from infinity to that point

Question 17

gravitational potential (Vg)

Answer 17

the work done in taking a unit mass from infinity to that point

Question 18

capacitance

Answer 18

ratio of charge stored to the potential difference between the plates of a capacitor

Question 19

dielectric

Answer 19

an insulating material that can be placed between the plates of a capacitor in order to increase its capacitance

Question 20

eddy currents

Answer 20

currents induced in the core of a transformer by the changing magnetic flux and cause energy losses by heating up the core

Question 21

Faraday’s law

Answer 21

the magnitude of an induced emf is proportional to the rate of change of flux linkage

Question 22

flux linkage

Answer 22

the product of the number of turns in a coil and the flux through the coil

Question 23

Lenz’s law

Answer 23

the direction of the induced end is such that if an induced current were to flow, it would oppose the change which caused it

Question 24

magnetic flux

Answer 24

is equal to BA cos θ, where B is magnetic field strength, A is area and θ is the angle between the field lines and the normal to the plane of area

Question 25

rectification

Answer 25

the conversion of alternating current to direct current

Question 26

rms current/voltage

Answer 26

the value of current or voltage is that would produce the same amount of power as the equivalent DC value

Question 27

time constant

Answer 27

the time taken for the voltage or current to fall to 37% of its maximum value during the discharge of capacitor

Question 28

becquerel

Answer 28

unit of activity - the number of radioactive particles being emitted per second

Question 29

de Broglie wavelength

Answer 29

the wavelength of a matter wave

Question 30

deep inelastic scattering

Answer 30

the scattering of high energy electrons off the quarks within the protons and neutrons of the nucleus

Question 31

Heisenberg's uncertainty principle

Answer 31

the simultaneous measurement of the position and momentum of a particle will always have some uncertainty

Question 32

pair production

Answer 32

the interaction of a photon with a nucleus that produces an elementary particle and its corresponding antiparticle

Question 33

photoelectric effect

Answer 33

the emission of electrons from a metal surface when light is shone upon it

Question 34

quantum tunneling

Answer 34

a process whereby quantum particles can overcome potential (energy) barriers deemed impossible according to classical physics

Question 35

stopping potential

Answer 35

the voltage at which electrons are brought to a halt as the electrical energy matches their kinetic energy

Question 36

threshold frequency

Answer 36

lowest frequency of a light that causes electron emission from a metal's surface

Question 37

wave function

Answer 37

the square of the wave function gives the probability per unit volume of finding the electron at that position

Question 38

work function

Answer 38

the minimum amount of energy needed by an electron to escape a metal's surface