Unit Fifteen Thermal Energy; Nuclear Energy; Modern Physics.

Unit FifteenUnit Fifteen

Thermal Energy;Thermal Energy;

Nuclear Energy; Nuclear Energy;

Modern PhysicsModern Physics

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy1. 1. TemperatureTemperature is the quantity that tells how is the quantity that tells how hot or cold something is compared to a hot or cold something is compared to a standard. It’s also the standard. It’s also the measure of the measure of the average internal kinetic energy of its average internal kinetic energy of its particlesparticles..

A. TheA. The kinetic theory of matterkinetic theory of matter states that, states that, if you increase something’s temperature, if you increase something’s temperature, its matter expands because the molecules its matter expands because the molecules

move faster. If you decrease itsmove faster. If you decrease its temperature, its matter contracts (shrinks) temperature, its matter contracts (shrinks) because the molecules move slower. because the molecules move slower.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy2. At the temperature of 2. At the temperature of absolute zeroabsolute zero, there is , there is

no molecular motion and no heat in the no molecular motion and no heat in the

substance.substance.

A. Absolute zero occurs when all atomic and A. Absolute zero occurs when all atomic and

molecular motion stops. molecular motion stops. This is the This is the

lowest temperature possiblelowest temperature possible. .

B. Absolute zero occurs at 0 Kelvin, or B. Absolute zero occurs at 0 Kelvin, or

– – 273.15273.15oo Celsius or at – 460 Celsius or at – 460oo Fahrenheit. Fahrenheit.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy

ooFF ooCC KK

Water Boils Water Boils 212 212 100 100

373 373

Room Temp Room Temp 72 72 23 23 296 296

Water Freezes Water Freezes 32 32 0 0 273 273

Absolute ZeroAbsolute Zero – – 460 460 – – 273 0273 0


3. 3. HeatHeat and and temperaturetemperature

are two concepts that are two concepts that

are often confused. are often confused.

They’re related to each They’re related to each

other because they are other because they are

both related to the both related to the

concept of concept of thermal thermal

energyenergy. .


A. A. HeatHeat is the thermal energy transfer from is the thermal energy transfer from

one object to another because of a one object to another because of a

temperature difference between these temperature difference between these

objects. objects.

B. Matter doesn’t contain heat. Matter B. Matter doesn’t contain heat. Matter

contains thermal energy. contains thermal energy. Heat is energy Heat is energy

in transitin transit..

C. C. HeatHeat may be defined as may be defined as energy that energy that

travels from a high temperature object travels from a high temperature object

to a lower temperature objectto a lower temperature object. .

D. Heat is a flow of thermal energy, it is not a D. Heat is a flow of thermal energy, it is not a

substance (matter) that flows.substance (matter) that flows.


Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy E. A material doesn’t possess heat. The E. A material doesn’t possess heat. The

appropriate term for the microscopic appropriate term for the microscopic

energy in an object is its energy in an object is its internal internal

(thermal) energy(thermal) energy..

F. A material’s internal (thermal) energy is F. A material’s internal (thermal) energy is

the total energy of the particles (including the total energy of the particles (including

their kinetic energy and their potential their kinetic energy and their potential

energy) in the material. energy) in the material.

Thermal equilibriumThermal equilibrium is is reached when two or reached when two or

more objects in contact with each other reach more objects in contact with each other reach

the same temperature. Heat no longer flows the same temperature. Heat no longer flows

between the objects because there is no between the objects because there is no

temperature difference between them.temperature difference between them.



Phase Changes / Changes of StatePhase Changes / Changes of State

Phase ChangePhase Change DescriptionDescription

Solid to Liquid - - - - - - - Solid to Liquid - - - - - - - MeltingMelting

Liquid to Solid - - - - - - - Liquid to Solid - - - - - - - FreezingFreezing

Liquid to Gas - - - - - - - Liquid to Gas - - - - - - - BoilingBoiling

Gas to Liquid - - - - - - - Gas to Liquid - - - - - - - CondensationCondensation

Solid to Gas - - - - - - - - Solid to Gas - - - - - - - - SublimationSublimation

Gas to Solid - - - - - - - - Gas to Solid - - - - - - - - DepositionDeposition


In the previous slide, when water moves from In the previous slide, when water moves from the bottom of the graph to the top of the graph the bottom of the graph to the top of the graph ((gets warmergets warmer), it ), it gains energygains energy in the form of in the form of heat (calories) heat (calories) from the surrounding from the surrounding environmentenvironment. .

When water moves from the top of the graph When water moves from the top of the graph to the bottom of the graph (to the bottom of the graph (gets coolergets cooler), it ), it loses energyloses energy in the form of heat (calories) in the form of heat (calories) to to the surrounding environmentthe surrounding environment. .

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal EnergyThe transfer of thermal energy from one The transfer of thermal energy from one

material to another can occur in three ways. material to another can occur in three ways.

1. By 1. By conductionconduction

2. By 2. By convectionconvection

3. By 3. By radiationradiation

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy1. 1. ConductionConduction is the transfer of thermal energy is the transfer of thermal energy in the form of heat from one substance to in the form of heat from one substance to another or from one part of a substance to another or from one part of a substance to another part of the same substance another part of the same substance by by direct contactdirect contact. . A. This form of transfer A. This form of transfer occurs most often occurs most often in solids in solids (i. e. a metal spoon gets hot (i. e. a metal spoon gets hot when left in a pot of boiling water).when left in a pot of boiling water). B. The kinetic energy is transferred from one B. The kinetic energy is transferred from one particle to another when the particles particle to another when the particles collide.collide.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy C. A wooden or plastic spoon would be an C. A wooden or plastic spoon would be an

example of a poor conductor or an example of a poor conductor or an

insulator. insulator.

D. An D. An insulatorinsulator delays the transfer of heat. delays the transfer of heat.

i. Some examples of insulators are i. Some examples of insulators are

wood, wool, straw, and paper. wood, wool, straw, and paper.

E. A poor conductor is a good insulator and E. A poor conductor is a good insulator and

vice versa. vice versa.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy2. 2. ConvectionConvection is the transfer of thermal energy is the transfer of thermal energy

by by the actual mass movement of heated the actual mass movement of heated

particlesparticles. .

A. Convection A. Convection only occurs in fluids only occurs in fluids

(liquids and gases)(liquids and gases)..

B. The molecules in a gas are far apart B. The molecules in a gas are far apart

because the bonds holding them together because the bonds holding them together

are weak. For this reason, a small energy are weak. For this reason, a small energy

input results in large movement. input results in large movement.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal EnergyBoiling pots of water and lava lamps provide Boiling pots of water and lava lamps provide graphic illustrations of convection. They are an graphic illustrations of convection. They are an excellent reminder of the process that drives the excellent reminder of the process that drives the movements of the ocean currents and the movements of the ocean currents and the movements of the atmospheric winds. movements of the atmospheric winds.

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal Energy3. Thermal energy transferred by 3. Thermal energy transferred by radiationradiation

occurs through space in the form of occurs through space in the form of

electromagnetic waves.electromagnetic waves.

A. Some examples are solar energy, light, A. Some examples are solar energy, light,

radio waves, microwaves radio waves, microwaves

Unit Fifteen: Thermal EnergyUnit Fifteen: Thermal EnergyConduction, convection, and radiation all occur Conduction, convection, and radiation all occur together in everyday life. together in everyday life.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy The Structure of MatterThe Structure of Matter

1. The smallest divisible portion of matter is the 1. The smallest divisible portion of matter is the atom. atom. 2. 2. Atoms are made up of electrons, protons, Atoms are made up of electrons, protons, and neutronsand neutrons. . 3. Protons and neutrons lie in the nucleus of 3. Protons and neutrons lie in the nucleus of the atom and electrons move around the the atom and electrons move around the nucleus of the atom.nucleus of the atom.4. Protons are positively charged (+), electrons 4. Protons are positively charged (+), electrons are negatively charged (-), and neutrons are negatively charged (-), and neutrons have no charge (neutral).have no charge (neutral).

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy

ParticleParticle Mass Mass Charge Charge

ElectronElectron 9.1094 x 109.1094 x 10-31-31 kg kg - 1 - 1

ProtonProton 1.6726 x 101.6726 x 10-27-27 kg kg + 1+ 1

NeutronNeutron 1.6749 x 101.6749 x 10-27-27 kg kg 0 0

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergyBecause the parts of an atom are so small and Because the parts of an atom are so small and electrons revolve around the nucleus of atoms,electrons revolve around the nucleus of atoms,we can not be sure of an electron’s exact we can not be sure of an electron’s exact location at an exact time like we can for larger location at an exact time like we can for larger objects like a baseball. This principle for very objects like a baseball. This principle for very tiny particles is called tiny particles is called The Uncertainty The Uncertainty PrinciplePrinciple and it states that it’s impossible to and it states that it’s impossible to measure the exact location of a particle at a measure the exact location of a particle at a certain time without altering its momentum and certain time without altering its momentum and vice versa. vice versa.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergySince it’s impossible to know a particle’s Since it’s impossible to know a particle’s momentum and position at the exact same time, momentum and position at the exact same time, we say that we say that electrons form a cloudelectrons form a cloud around the around the nucleus. All this means is that the electron is nucleus. All this means is that the electron is probably in a certain location around the probably in a certain location around the nucleus. nucleus.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy5.5. The The atomic numberatomic number of an atom is the of an atom is the number of protons in its nucleus.number of protons in its nucleus. A. A. The properties of an element are The properties of an element are defined by its atomic numberdefined by its atomic number.. B. The atomic number also represents B. The atomic number also represents number of electrons in a neutral atom.number of electrons in a neutral atom.6. The6. The mass numbermass number of an atom is the the total of an atom is the the total number of protons plus neutrons in the number of protons plus neutrons in the nucleus.nucleus.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy7.7. Isotopes Isotopes are atoms of the same element are atoms of the same element

(with the same number of protons) but with (with the same number of protons) but with

different numbers of neutrons.different numbers of neutrons.

A. Examples: A. Examples:

carbon – 12 carbon – 12

(6 protons, 6 electrons, (6 protons, 6 electrons, 6 neutrons6 neutrons) )

carbon – 14 carbon – 14

(6 protons, 6 electrons, (6 protons, 6 electrons, 8 neutrons8 neutrons))

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy8. Two forces that act on subatomic particles 8. Two forces that act on subatomic particles (protons, neutrons, and electrons) (protons, neutrons, and electrons)

A. The A. The electrical forceelectrical force is an attractive force is an attractive force

that acts between the electrons around that acts between the electrons around the nucleus and the protons in the the nucleus and the protons in the nucleus. Positively (+) charged protons nucleus. Positively (+) charged protons attract negatively (–) charged electrons. attract negatively (–) charged electrons.

B. The B. The strong nuclear forcestrong nuclear force is an attractive is an attractive force that only works with protons and force that only works with protons and neutrons. It only works when they are neutrons. It only works when they are

very close together in the nucleus of very close together in the nucleus of atoms. atoms.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy9. On the Periodic Table, the 9. On the Periodic Table, the smaller smaller elements elements (near the top) have about the (near the top) have about the same number of protons and neutrons same number of protons and neutrons (about a 1:1 ratio). They (about a 1:1 ratio). They tend to be stabletend to be stable.. The The larger elementslarger elements (near the bottom) (near the bottom) have more neutrons than protons (about a have more neutrons than protons (about a 1.5:1 ratio). They 1.5:1 ratio). They tend to be unstable tend to be unstable (too (too many unstable neutrons). many unstable neutrons). 10. These large, unstable elements undergo 10. These large, unstable elements undergo a a natural processnatural process calledcalled radioactive decayradioactive decay so they can become more stable. so they can become more stable.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy11. A 11. A nuclear reactionnuclear reaction (involving the atom’s (involving the atom’s

nucleus, not just its electrons as in a nucleus, not just its electrons as in a

chemical reaction) results when an unstable chemical reaction) results when an unstable

nucleus breaks down and emits radioactive nucleus breaks down and emits radioactive

particles in its natural attempt to become particles in its natural attempt to become

more stable.more stable.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy12. There are 12. There are three types of particles / rays three types of particles / rays

released during radioactive decayreleased during radioactive decay. .

A. A. alpha particle (alpha particle (αα))

i. i. helium nucleus (+ 2 charge) helium nucleus (+ 2 charge)

ii. largest, slowest, least penetrating ii. largest, slowest, least penetrating

particle; stopped by a few sheets of particle; stopped by a few sheets of

thin paper thin paper

iii. iii. released duringreleased during alpha decayalpha decay

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy B. B. beta particle (beta particle (ββ))

i. fast moving electron (i. fast moving electron (– 1 charge) – 1 charge)

ii. smaller and more penetrating than ii. smaller and more penetrating than

alpha particle; stopped by several alpha particle; stopped by several

sheets of aluminum foil sheets of aluminum foil

iii. iii. released during beta decayreleased during beta decay

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy C. C. gamma radiation (gamma radiation (γγ))

i. i. no particle, no mass or charge, only no particle, no mass or charge, only

high energy electromagnetic energyhigh energy electromagnetic energy

ii. ii. most penetrating and most damaging; most penetrating and most damaging;

stopped by leadstopped by lead

iii. always released during radioactive iii. always released during radioactive

decay of any kinddecay of any kind

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear Energy13. The 13. The half lifehalf life of a radioactive isotope is the of a radioactive isotope is the

time it takes for one half of the isotope to time it takes for one half of the isotope to

decay (change from one element into a decay (change from one element into a

more stable element).more stable element).

A. Example: The half life of mercury - 195 is A. Example: The half life of mercury - 195 is

31 hours. If you start with 20 g of 31 hours. If you start with 20 g of

mercury - 195, how much will be left after mercury - 195, how much will be left after

31 hours? (10 g) How much will be left 31 hours? (10 g) How much will be left

after 62 hours? (5 g) after 62 hours? (5 g)

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergyWhen an When an alpha particle (alpha particle (αα)) is emitted from a is emitted from a radioactive element, the element’s mass radioactive element, the element’s mass number decreases by 4 and its atomic number number decreases by 4 and its atomic number decreases by 2 as shown in the equation below.decreases by 2 as shown in the equation below.

226226 8888

Ra Ra →→4422

He +He + 222222 8686

RnRn

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergyWhen a When a beta particle (beta particle (ββ)) is emitted from a is emitted from a radioactive element, the element’s mass radioactive element, the element’s mass number remains unchanged and its atomic number remains unchanged and its atomic number increases by 1 as shown in the number increases by 1 as shown in the equation below.equation below.

209209 8282

Pb Pb →→ 00–– 11

e +e + 209209 8383

BiBi

The neutron turns into a proton and an electron.The neutron turns into a proton and an electron.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergyWhen a When a gamma ray (gamma ray (γγ)) is emitted from a is emitted from a nuclear reaction, the mass number and atomic nuclear reaction, the mass number and atomic number of the involved nucleus remain number of the involved nucleus remain unchanged since gamma rays are pure energyunchanged since gamma rays are pure energyand have no mass. and have no mass.

Unit Fifteen: Nuclear EnergyUnit Fifteen: Nuclear EnergyNuclear FissionNuclear Fission is the splitting of large is the splitting of large

unstable (usually uranium) nuclei resulting in a unstable (usually uranium) nuclei resulting in a

tremendous release of energy.tremendous release of energy.

Nuclear FusionNuclear Fusion is the combining of small is the combining of small

nuclei resulting in an even greater release of nuclei resulting in an even greater release of

energy. energy. The sun uses nuclear fusion to The sun uses nuclear fusion to

produce energyproduce energy. .

1. With nuclear fusion, 2 hydrogen atoms 1. With nuclear fusion, 2 hydrogen atoms

combine to form 1 helium atom.combine to form 1 helium atom.


A A nuclear fission power plantnuclear fission power plant uses a uses a

controlled nuclear fission reaction to boil controlled nuclear fission reaction to boil

(superheat) water. This steam is then used to (superheat) water. This steam is then used to

turn a turbine that is connected to a generator. turn a turbine that is connected to a generator.

This generator converts the mechanical energy This generator converts the mechanical energy

of the turbine into electrical energy. This of the turbine into electrical energy. This

electrical energy is then sent out to its electrical energy is then sent out to its

customers. customers.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsThere are several oddities about light that we There are several oddities about light that we will discuss in this last section of the course. will discuss in this last section of the course.

1. One is that 1. One is that light has both particle-like light has both particle-like properties and wave-like propertiesproperties and wave-like properties..

2. Another is that 2. Another is that the speed of light is the speed of light is constant in a vacuumconstant in a vacuum..

We will discuss the particle and wave We will discuss the particle and wave properties of light first. properties of light first.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics1.1. One of the ways One of the ways light exhibits wave-like light exhibits wave-like

properties is its ability to show properties is its ability to show constructive and destructive interference constructive and destructive interference patternspatterns. We know that waves of any kind . We know that waves of any kind exhibit interference patterns. exhibit interference patterns. A. A. Double slit interferenceDouble slit interference occurs when occurs when light of one frequency (one color) is shown light of one frequency (one color) is shown through two narrow, closely spaced slits. through two narrow, closely spaced slits. When this is done, light (constructive – When this is done, light (constructive – crest to crest interference) and dark crest to crest interference) and dark

(destructive – crest to trough interference) (destructive – crest to trough interference) bands will appear on a screen. bands will appear on a screen.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsDouble slit interferenceDouble slit interference is shown here. is shown here. This This shows the wave-like properties of lightshows the wave-like properties of light. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics2. One of the ways 2. One of the ways light shows particle-like light shows particle-like properties is by the photoelectric effectproperties is by the photoelectric effect..

This occurs with the ejection of electrons This occurs with the ejection of electrons from certain photosensitive metals when from certain photosensitive metals when light falls upon themlight falls upon them..

A.A. The photoelectric effect suggests that The photoelectric effect suggests that light travels as a wave but it interacts light travels as a wave but it interacts

with matter as a stream of particles with matter as a stream of particles (photons). (photons).

B. Photons are discrete little bundles of light B. Photons are discrete little bundles of light energy. energy.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics

light rayslight rays

photosensitive metalphotosensitive metal

electronselectrons

The Photoelectric EffectThe Photoelectric Effect is shown here. is shown here. This This shows the particle-like properties of lightshows the particle-like properties of light..

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsRemember from the beginning of the semester, Remember from the beginning of the semester, that all motion is relative. Motion depends on that all motion is relative. Motion depends on your frame of reference. For example, if a your frame of reference. For example, if a baseball is thrown at 60 mph at you from a baseball is thrown at 60 mph at you from a stationary truck, the baseball will be traveling at stationary truck, the baseball will be traveling at 60 mph when you catch it. If the truck is moving60 mph when you catch it. If the truck is movingtoward you at 40 mph when the baseball is toward you at 40 mph when the baseball is thrown at you at 60 mph, the baseball will be thrown at you at 60 mph, the baseball will be traveling at 100 mph when you catch it. traveling at 100 mph when you catch it.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsSimilarly, if the truck is moving away from you Similarly, if the truck is moving away from you at 40 mph when the baseball is thrown toward at 40 mph when the baseball is thrown toward you at 60 mph, the baseball will be traveling at you at 60 mph, the baseball will be traveling at 20 mph when you catch it. The baseball has 20 mph when you catch it. The baseball has three different speeds depending on the frame three different speeds depending on the frame of reference. of reference.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics1.1. Another oddity of light, as mentioned above, Another oddity of light, as mentioned above, is that, no matter what your relative motion is is that, no matter what your relative motion is to a light source (approaching it or moving to a light source (approaching it or moving away from it), away from it), the speed of light always the speed of light always remains constant in a vacuumremains constant in a vacuum. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsPeople think of space and time as two separate People think of space and time as two separate quantities. quantities. Albert Einstein thought of space Albert Einstein thought of space and time as linked together, or as two parts and time as linked together, or as two parts of one whole, called space-timeof one whole, called space-time..1. He surmised that space and time do not exist 1. He surmised that space and time do not exist outside the universe. Space and time only outside the universe. Space and time only exist within the universe.exist within the universe.2. He also surmised that 2. He also surmised that space and time are space and time are linked together by the speed of light, linked together by the speed of light, since the speed of light is always since the speed of light is always constantconstant. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics

2. To understand this, instead of thinking as 2. To understand this, instead of thinking as though you are moving through time or though you are moving through time or moving through space, think of moving moving through space, think of moving through a combination of through a combination of space-timespace-time. . A. A. When you stand still, you are only When you stand still, you are only moving through time and not through moving through time and not through spacespace.. B. When you move a little, you are moving a B. When you move a little, you are moving a little bit through space, but you are still little bit through space, but you are still mostly moving through time. mostly moving through time.

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics C. However, when you are moving at the C. However, when you are moving at the speed of light, you are traveling completely speed of light, you are traveling completely through space and not through time. through space and not through time. Therefore, Therefore, light is timeless and if you light is timeless and if you were traveling at the speed of light, you were traveling at the speed of light, you would experience no forward motion of would experience no forward motion of timetime.. D. D. Therefore, time slows down for you as Therefore, time slows down for you as you approach the speed of lightyou approach the speed of light. . E. In summary, E. In summary, time slows down as you time slows down as you approach the speed of lightapproach the speed of light. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern PhysicsSince space and time are linked as discussed Since space and time are linked as discussed above, not only does time change as you above, not only does time change as you approach the speed of light, but approach the speed of light, but space also space also changes as you approach the speed of lightchanges as you approach the speed of light..1. 1. When an object approaches the speed of When an object approaches the speed of light, its length contracts along the light, its length contracts along the direction of its motiondirection of its motion. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics1. There are some very large objects in the 1. There are some very large objects in the universe, such as large stars, that have very universe, such as large stars, that have very large forces of gravity. large forces of gravity. These forces of These forces of gravity can be so large that they can even gravity can be so large that they can even bend nearby light rays toward thembend nearby light rays toward them. .

Unit Fifteen: Modern PhysicsUnit Fifteen: Modern Physics2. A black hole is the result of a very large star 2. A black hole is the result of a very large star that collapses onto itself. When this occurs, that collapses onto itself. When this occurs, gravity pulls its immense mass together to gravity pulls its immense mass together to the point that it becomes almost infinitely the point that it becomes almost infinitely dense. With this immense density, dense. With this immense density, the the gravity field of the black hole becomes so gravity field of the black hole becomes so strong that nothing nearby can escape it strong that nothing nearby can escape it – – not even lightnot even light. This is the reason why we . This is the reason why we can’t see black holes. We only see the can’t see black holes. We only see the effects of black holes on the surrounding effects of black holes on the surrounding environment. environment.

The EndThe End

Unit Fifteen Thermal Energy; Nuclear Energy; Modern Physics.

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Transcript of Unit Fifteen Thermal Energy; Nuclear Energy; Modern Physics.