Transport of Radiant Energy - Aphy 140 Lecture 3 Quiz

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Questions and Answers

According to Wien's Law, how is the wavelength at which energy is emitted per unit wavelength related to the absolute temperature of an object?

No relation

Directly proportional

Proportional to the square root

Inversely proportional (correct)

What does Wien's Law suggest about the value of E(λ) at the wavelength λm?

Proportional to λm

Proportional to λm^5 (correct)

Not related to λm

Constant

In Stefan's Law, how is the rate of energy emission from a full radiator related to its absolute temperature?

Quadratic relationship

Proportional to the fourth power (correct)

Cubic relationship

Linear relationship

What is the Stefan-Boltzmann constant σ used for in Stefan's Law?

Quantifying the rate of energy emission from a full radiator Signup and view all the answers

According to Wien's Law, what happens to the spectra peaks of objects with different temperatures?

They shift to shorter wavelengths Signup and view all the answers

How is the value of E(λ) at the wavelength λm related to temperature according to Wien's Law?

Proportional to temperature to the power -5 Signup and view all the answers

What are the three main sources of radiation mentioned in the text?

Particles shot into space during solar flares Signup and view all the answers

Which factor does NOT affect the amount of space radiation an astronaut may be exposed to while orbiting the Earth?

Distance from the Moon Signup and view all the answers

What is the concept of 'absorptivity' related to in the context of radiation?

The fraction of incident radiation absorbed at a specific wavelength Signup and view all the answers

What is the special case when the emissivity of an object is 1 at all wavelengths?

Black body spectrum Signup and view all the answers

In what range are nearly all the radiation emitted by full radiators confined to?

$3-100$ μm Signup and view all the answers

What causes the absorptivity and emissivity of a gas to change with height in the lower atmosphere?

Pressure changes Signup and view all the answers

What is the velocity of electromagnetic radiation?

3.0 × 10^8 m/s Signup and view all the answers

Which type of radiation has enough energy to move atoms in a molecule but not enough to cause chemical changes?

Non-Ionizing Radiation Signup and view all the answers

What type of radiation is commonly used to kill cancer cells?

Gamma Radiation Signup and view all the answers

Which law describes the relationship between the temperature of an object and the wavelength at which it emits the most radiation?

Wien's Law Signup and view all the answers

What is the form of subatomic particles or waves through which ionizing radiation travels?

Photons Signup and view all the answers

Which property of radiation is used in many manufacturing processes?

Ionization Signup and view all the answers

Study Notes

Wien's Law

The wavelength at which energy is emitted per unit wavelength (λm) is inversely proportional to the absolute temperature (T) of the object.
Wien's Law suggests that the value of E(λ) at the wavelength λm is at a maximum.

Stefan-Boltzmann Law

The rate of energy emission from a full radiator is proportional to the fourth power of its absolute temperature.
The Stefan-Boltzmann constant (σ) is used to convert the temperature in Kelvin to the rate of energy emission in Watts per square meter.

Radiation Spectra

According to Wien's Law, objects with different temperatures have different spectra peaks. Higher temperature objects have their spectra peaks shifted towards shorter wavelengths and vice versa.
The value of E(λ) at the wavelength λm is directly proportional to the fourth power of the temperature according to Wien's Law.

Sources of Radiation

The three main sources of radiation are the sun, the earth, and space.

Space Radiation

The amount of space radiation an astronaut may be exposed to while orbiting the Earth is NOT affected by the astronaut's altitude.

Absorptivity

Absorptivity is related to the fraction of incident radiation that is absorbed by an object.

Emissivity

When the emissivity of an object is 1 at all wavelengths, it is considered a blackbody, which absorbs and emits all radiation.

Radiation Range

Nearly all the radiation emitted by full radiators is confined to the infrared range.

Atmospheric Radiation

The absorptivity and emissivity of a gas in the lower atmosphere change with height due to variations in gas concentration and pressure.

Electromagnetic Radiation

Electromagnetic radiation travels at the speed of light (c) which is approximately 3 x 10⁸ m/s.

Radiation Types

Radiation that has enough energy to move atoms in a molecule but not enough to cause chemical changes is called non-ionizing radiation.
Radiation that has enough energy to remove electrons from atoms is called ionizing radiation, and a common type used to kill cancer cells is gamma radiation.

Radiation Laws

The relationship between an object's temperature and the wavelength at which it emits the most radiation is described by Wien's Displacement Law.

Ionizing Radiation

Ionizing radiation travels as subatomic particles or electromagnetic waves.

Manufacturing

The property of radiation heat transfer is used in many manufacturing processes, such as drying, heating, and curing.

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Description

Test your knowledge on the origin and nature of radiation, absorption and emission of radiation, full or black body radiation, Wien's Law, Stefan's Law, Planck's Law, spatial relations, cosine law for emission and absorption, reflection, radiance and irradiance, and attenuation of a parallel beam.