## IB Physics Glossary

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### C

#### Capacitance

is the ratio of charge to potential difference or voltage,

$C=\frac{Q}{V}$.

 Keyword(s): 11

#### CCD

is a charged coupled device such that the amount of charge that builds up on one of its pixels is proportional to the light intensity falling on the pixel.
The photoelectric effect is responsible for conversion of photons energy to electron energy.
 Keyword(s): 14.2

#### CCD resolution

is possible if the size of an image covers at least two pixels.
 Keyword(s): 14.2

#### CD/DVD pit depth

is given by $d = \frac{\lambda}{4}$where $\lambda$ is the wavelength of the laser for the CD/DVD reader.The distance corresponds to a total additional distance of $\frac{\lambda}{2}$ travelled by the laser light at a pit-land interface (corresponding to binary 1).
DVDs (shorter pit length and double layers) have about 7 times the storage capacity of CDs. Changing or reducing the laser wavelength can increase the resolution, by decreasing $\theta= 1.22 \frac{\lambda}{b}$, thus allowing more pits and therefore greater storage capacity. Bluray technology uses shorter wavelength laser light.
 Keyword(s): 14.1

#### Chandrasekhar core limit

equals 1.4 solar masses for the core of a (super) red giant.

Low mass stars: core mass < 1.4 solar masses
Red giant -> Planetary nebula -> White dwarf
Helium burns and fuses in the core into carbon and oxygen.

High mass stars: core mass > 1.4 solar masses
Super Red Giant -> Supernova -> Neutron star or Black Hole
Silicon burns and fuses in the core into iron.
 Keyword(s): E5

#### Circular motion

occurs under the following conditions:
• the force $F$, and therefore acceleration $a$, and change in velocity $\Delta v$, is directed towards the center of a circle;
• the velocity is perpendicular to the force, $v \perp F$.

Data booklet reference:﻿

﻿$\nu \; = \;\omega r$
$a\; = \;{{{v^2}} \over r}\; = \;{{4{\pi ^2}r} \over {{T^2}}}$
$F\; = \;{{m{v^2}} \over r}\; = \;m{\omega ^2}r$
 Keyword(s): 6.1

#### Coefiicient of voume expansion

$\gamma$, is the fractional change in volume of a substance $\frac{\Delta V}{V}$ per unit degree change in temperature $\Delta T$:
$\gamma = \frac{\Delta V}{V \times \Delta T}=\frac{V_2-V_1}{V_1 \times (T_2-T_1)}$.
The SI unit is K-1.

For problems involving rise in sea level
• height, h, of water can be found from
$h = \frac{Volume}{Area}$
• rise is seal level can be calculated using
$\Delta h = \gamma \times h \times \Delta T$.
 Keyword(s): 8.6

#### Comets

have
a. highly elliptical orbits;
b. large orbital radii beyond planets;
c. orbit are in many different planes. (d)
 Keyword(s): E1

#### Conductive hearing loss

occurs when the air conduction thresholds (middle ear) show a hearing loss but the bone conduction thresholds (cochlea) are normal. Reasons include
1. blockages - build up of wax of fluid;
2. accidents - damaged middle ear or ruptured eardrum;
3. diseases/infection - middle ear bones are prevented from moving;
4. age - bones in middle ear become solidified with age.
 Keyword(s): I1

#### Conductor

﻿A material that allows the flow of electric charge through it.
Conduction is the flow of charge (free electrons) from atom to atom within a material.

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