Temperature

What types of scales are celsius and fahrenheit?

Reference scales for measuring temperature, relative to two common reference points (freezing & boiling), can go above and below these

What type of scale is kelvin?

- Absolute scale

- Begins at absolute zero (-273.15°C)

- Theoretically no molecular activity, no energy, to radiation emitted

Convert celsius to fahrenheit

(°C x 9/5) + 32

Convert fahrenheit to celsius

(°F - 32) x 5/9

Convert celsius to kelvin

°C + 273.15

Convert fahrenheit to kelvin

((°F - 32) x 5/9) + 273.15

Why are freezing and boiling points for celsius and fahrenheit different?

- Different scientific method used to get the scale

- Celsius based on fresh water

- Fahrenheit based on salt water

What is temperature?

- Average amount of kinetic energy potential/molecular activity in a volume

- Hotter objects produce/emit more radiation absorbed into out own bodies increasing out kinetic energy

- Ability of a substance to transfer energy to another substance as radiation

What is heat?

Energy in the process of being transferred

What is radiation?

Energy emitted as electromagnetic waves (all substances emit this above absolute zero)

How does the molecular structure of an object relate to its temperature?

- Gas has more energy

- Fewer molecular bonds

- Moves more than a solid

- Molecules collide more

- It will be hotter

What is the Stefan Boltzmann law?

Intensity of energy radiated by a black body increases according to the fourth power of its absolute temperature (hotter the temperature, the more energy you emit, exponential increase)

What is Wein's law?

Radiating body, wavelength of peak emissions inversely proportional to absolute temperature (increased temperature, shorter wavelength, radiation type can change)

What are peak emissions?

Range of wavelength where most of the radiative emissions are found

What is a black body?

- Theoretical

- Perfect emitter

- 100% of radiative energy emitted at an absolute temperature

- Emissivity 1.0 or 100%

What is a grey body?

- All bodies in nature

- Imperfect emitter

- Gives a proportion of maximum output at a temperature

What is emissivity?

Proportion of substances theoretical black body emissions that is emitted (0.8 = 80% of black body ideal)

How do radiation emissions react to changes in a substance's temperature in relation to Stefan Boltzmann and Wein's law?

Difference temperatures change the amount and types of radiation emitted

How does the sun's radiation emissions relate to Stefan Boltzmann and Wein's law?

- Sun gives more energy

- 64 milllion Wm2

- Short peak wavelengths

- 4 different types of radiation (ultraviolet, visible light, near infrared, infrared

How does the earth's radiation emissions relate to Stefan Boltzmann and Wein's law?

- Less energy

- 390 Wm2

- Longer peak wavelengths

- Near infrared and infrared radiation

What is solar radiation?

Radiation emitted by the sun

What are the approximate wavelengths of solar radiation?

- Infrared (45%), 0.8 um to 1 mm

- Visible light (45%), 0.4 to 0.8 um

- UV (10%), <0.4 um

What is terrestrial radiation?

Radiation emitted by the earth

What is the approximate wavelength for terrestrial radiation?

3 to 100 um