G11║ Physics T3 Q1

Dark materials are good _______ of radiation. They can reflect a little radiant energy.

absorbers

Radiant energy

any energy transmitted by radiation

_________ object is a perfect absorber. It reflects no radiant energy and appears perfectly black

matte or dull black

•Conduction and convection requires _________.

matter

infrared thermometer

measures the infrared radiant energy emitted by a body and converts it to temperature

Convection is heat transfer by _________.

moving fluids

Why is air a bad conductor?

particles are far apart, and the bonds between them are weak, so they need extra time to transfer energy from one place to another

A vaccuum between the silver layers

prevents heat leaving by conduction and convection, as these processes cannot take place in a vacuum

Earth loses heat primarily by _______

radiation

the transfer of heat that doesn't require matter. It is the way heat and light travel to us from the sun

radiation

longest wavelength shortest wavelength

radio wave gamma rays

Solar radiation reaches the earth's surface as _________________

ultraviolet, light and infrared radiation

The spontaneous transfer of heat is always from ______ objects to ______ objects.

warmer, cooler

the gases that are mainly responsible for this green house effect are ________

water vapor and carbon dioxide

Material containing trapped air, _______________ are good insulators.

wool, plastic foam and fiber glass

Insulated stopper (plastic)

•Reduces heat loss by conduction (plastic is a poor conductor) •It prevents convection current from escaping from the flask.

What do all all electromagnetic waves share?

•They are all transverse •They can all travel through a vacuum •They all travel at the same speed in a vacuum

Double glass silver layers

•reduces heat loss by radiation •(Silver surfaces are good reflectors)

•Earth emits radiation with maximum intensity at _____

10μm

black body

A body that is a perfect absorber of radiation and therefore emits a continuous spectrum of wavelengths

What is the difference between a conductor and an insulator?

A conductor is good at conducting thermal energy. An insulator is poor at conducting thermal energy.

Emissivity

Ability to radiate compared to that of black body at the same temperature and with the same surface area

Black cup cools down more quickly. Why?

An object with a dark surface will emit infrared radiation faster than an object with a light surface.

terrestrial radiation

Long wavelength radiation emitted by the earth

Stefan -Boltzmann law

Radiant energy emitted from a surface is proportional to the fourth power of its absolute temperature.

shortwave radiation

Sun's radiation or solar radiation

Factors affecting the rate of cooling

Surface area to volume ratio Emissivity Temperature difference between the object and its surrounding.

Radiation

The flow of heat in the form of electromagnetic waves.

Convection

The process of heat transfer from one location to the next by the movement of fluids. The moving fluid carries energy with it.

A good reflector of radiation is a . a poor absorber of radiation. b . a good absorber of radiation. c . a good emitter of radiation. d . none of the above

a

All objects emit and absorb infrared radiation. a) true b) false

a

Conduction can occur in liquid, gaseous or solid objects. a) true b) false

a

Conduction occurs in all forms of matter. Solids, liquids and gases. a) true b) false

a

Good reflectors are poor absorbers a) true b) false

a

Greenhouse gases absorb and re-emit much of this long-wavelength terrestrial radiation back to Earth. a) true b) false

a

If the materials are in the same room, they should have the same temperature, room temperature. a) true b) false

a

In a florist's greenhouse, glass acts as a one-way valve, letting a . high-frequency light in and preventing low frequency radiation from escaping. b . low-frequency light in and preventing high frequency radiation from escaping. c . none of the above

a

Newton's law of cooling says that the rate of cooling depends on a. the temperature difference between an object and its surroundings. b. the volume of an object. c. the mass of an object. d. the specific heat capacity of an object. e. all of the above

a

Sun emits radiation over a broad range of electromagnetic waves including the full range of visible light a) true b) false

a

The colder an object's surroundings, the ______ the object will cool. a) faster b) slower

a

The larger the ratio, the ____ the object cools. a) faster b) slower

a

The metallic coating on the glass surfaces of a Thermos vacuum bottle reduces the amount of energy transferred by a . radiation. b . conduction. c . convection. d . friction

a

When heat is added to matter, it makes the molecules speed up and bump into one another. This is known as... a) conduction b) convection c) radiation d) none of the mentioned are correct

a

When particles heat up and jiggle faster, carrying the heat energy with them is know as... a) convection b) conduction c) radiation d) all of the mentioned are correct

a

Which cools at the faster rate, a pot of boiling water left at room temperature or a pot of lukewarm water the same size left at room temperature? a. The boiling water. b. The lukewarm water. c. Neither—the cooling rate is the same for both

a

Which heats and cools quicker, land or water? a) Land b) Water

a

Which is true about the way the air flows? a) from high pressure to low pressure b) from law density to high density c) from low pressure to high pressure d) from top to bottom only

a

Kirchhoff's law

a good absorber of a given wavelength is also a good emitter of that wavelength. "Things around us approach thermal equilibrium only because good absorbers are also good emitters".

All objects around us emit radiation in ____________.

a mixture of wavelengths

A cup of hot coffee will cool faster if it a . has cream in it. b . is black.

b

Air is a very good conductor. a) true b) false

b

Earth reflects the energy in the short wavelength IR radiation and re-emits much of it as long-wavelength radiation. a) true b) false

b

Global warming by the greenhouse effect mostly results from the fact that an atmosphere with excess carbon dioxide is less transparent to a . solar radiation. b . terrestrial radiation. c . Neither of the above.

b

Heat travels from the sun to Earth by a . conduction. b . radiation. c . convection. d . insulation. e . vacuumization.

b

Planet Earth loses heat primarily by a . conduction. b . radiation. c . convection. d . all of these

b

Plastic foam is a good heat a. conductor. b. insulator. c. emitter. d. absorber. e. radiator.

b

Radiation from the sun often gets trapped in Earth's atmosphere. The reason for this is that a. radiation from the sun comes in at an angle to Earth. b. long-wavelength radiation is absorbed by the atmosphere. c. radiation from the sun gets reflected from Earth's atmosphere. d. the atmosphere allows only visible light to enter. e. the atmosphere allows only visible and infrared light to enter.

b

Uneven heating of Earth's surface creates ... a) Global Warming b) Convection Currents c) Global Winds d) Seasons

b

Warm air rises and the cool air sinks demonstrates this type of heat transfer. a) Conduction b) Convection c) Radiation d) Induction

b

Why is the cooling unit placed at the top of the refrigerator? a) Cold air rises b) Cold air sinks c) Hot air sinks d) Hot and cold air mix

b

wave theory predicted that the intensity should ________ as the wavelength ________ a) increased, increased b) increased, decreased c) decreased, increased d) decreased, decreased

b

All insulators can totally stop heat from getting through it. a) true b) false

b Insulators only delay the transfer of heat.

For conduction to take place between two objects, they must _________.

be touching each other

the best absorbers and emitters of radiation are

black matte materials

Electromagnetic spectrum

broad family of electromagnetic waves

A good absorber of radiation is . a good reflector. b . a poor emitter of radiation. c . a good emitter of radiation. d . none of the above

c

The reason light-colored clothes help keep you cool in warm weather is that clothes of light color a. weigh less. b. have a lot of spaces in them. c. reflect a lot of energy. d. absorb energy, leaving little to pass through. e. all of the above

c

Warm air is __________ dense than cold air and __________ creating convection currents. a) Less , sinks b) more , rises c) less, rises d) more, sinks

c

How does conduction transfer heat?

collisions between particles transfer thermal energy, without any overall transfer of matter

Heat can be transferred by ___________, ____________, and _______________.

conduction, convection, radiation.

In ________, heat is transferred by the vertical movement of the heated fluid itself.

convection

The heat inside the Earth's core due to nuclear reactions causes stones and minerals to melt and create a viscous fluid known as a plastic fluid. This fluid circulates, forming what we call _________.

convection currents

Energy transfer by convection is primarily restricted to a . gases. b . liquids. c . solids. d . fluids. e . none of the above

d

Heat transfer by conduction in metals occurs when a) atoms give off heat in the form of electromagnetic waves. b) large numbers of atoms move from place to place. c) electromagnetic waves travel from one place to another through a vacuum. d) electrons bump into atoms and other electrons.

d

Heat transfer by convection occurs when a. electromagnetic waves travel from one place to another through a vacuum. b. electrons bump into other electrons. c. atoms give off heat in the form of electromagnetic waves. d. large numbers of atoms move from place to place. e. none of the above

d

The lower atmosphere is directly warmed a . by the emission of terrestrial radiation. b . by incoming solar radiation. c . from the weight of the atmosphere. d . by absorption of terrestrial radiation

d

_________________ travels in the form of electromagnetic waves. a) Electrical energy b) Thermal energy c) Chemical energy d) Light energy

d

The __________ container would be the warmest after ten minutes because its surface absorbs heat _______ the best. The _________ container would be the coolest because it is the poorest at __________ heat radiation.

dull black, energy, shiny metal, absorbing

The reason you can hold your fingers beside a candle flame without getting hurt is that a. air convects heat well. b. hot air rises. c. air is a poor heat conductor. d. hot-air convection currents travel upward. e. all of the above

e

The word radiation refers to __________ waves.

electromagnetic

At thermal equilibrium, the emission rate must ____ the absorption rate. Objects absorb radiant energy as much as they emit

equal

•Air in contact with a hot stove ____ and becomes ____ dense.

expands, less

Convection occurs in ________ because molecules can move .

fluids (liquids and gases)

Metals are the best conductors because they have

free electrons

Poor conductors are _______ insulators

good

at low wavelengths, the intensity should become ______

infinite

Shiny surfaces are good ___________ of radiation

reflectors

The __________ container would be the warmest after ten minutes because its shiny surface reflects heat _______ back into the container so less is lost. The ________ container would be the coolest because it is the best at _______ heat radiation.

shiny metal, energy, dull black, emitting

The hotter the object, the _____ the wavelength of the waves it emits.

shorter

the radiation of a black body emits depends on the ________ of the body

temperature

What is meant by saying cold is not a tangible thing?

the cold is a process of energy loss so it's a feeling not something tangible

What are the role of "loose" electrons in heat conductors?

the electrons are free to move and the higher energy electrons will pump the lower energy electrons loosing some of its energy, this energy will be gained by the lower energy electrons

Visible Light waves

the only type of radiation we can see

Conduction of heat

the transfer of energy within materials and between different materials that are in direct contact

Greenhouse effect

the warming of the atmosphere caused by trapped solar radiation

Wien's Displacement Law

the wavelength of maximum emission is inversely proportional to the absolute temperature; if you double the temp., the wavelength is halved

Infrared waves

thermal radiation, transfer heat energy

Solids have ______, atoms vibrate faster and pass on energy in less time.

tighter bonds

What is radiant energy?

transfer of heat as an electromagnetic energy

The atmosphere is __________ to the short-wavelength IR radiation from the sun.

transparent