Blackbody Radiation: Master Thermal Radiation from Perfect Emitters

Question 1

Which of the following statements is **NOT** true about a blackbody?

Accepted Answer

It absorbs only specific wavelengths of radiation.

Answer

It emits radiation at all wavelengths.

Answer

It absorbs all incident radiation, regardless of wavelength.

Answer

Its emission spectrum is continuous.

Question 2

At what wavelength does the spectral intensity of blackbody radiation reach its peak?

Accepted Answer

The wavelength at which the spectral intensity of blackbody radiation is maximum is inversely proportional to the temperature of the blackbody, as described by Wien's displacement law.

Answer

The peak wavelength is directly proportional to the temperature of the blackbody, according to Planck's law.

Answer

The peak wavelength remains constant regardless of the blackbody's temperature.

Answer

The peak wavelength is independent of the temperature and is a fixed value.

Question 3

The total emissive power of a blackbody at a given temperature is:

Accepted Answer

Proportional to the fourth power of its absolute temperature.

Answer

Independent of its absolute temperature.

Answer

Proportional to the reciprocal of its absolute temperature.

Answer

Proportional to the square of its absolute temperature.

Question 4

What is the characteristic shape of the spectral distribution of blackbody radiation?

Accepted Answer

A continuous spectrum with a peak wavelength that shifts to shorter wavelengths as the temperature increases.

Answer

A discrete spectrum with a constant peak wavelength regardless of temperature.

Answer

A spectrum with multiple peaks, with the number of peaks increasing with temperature.

Answer

A uniform spectrum with no distinct peak wavelength.

Question 5

Which of the following is a limitation of the blackbody model when applied to real-world objects?

Accepted Answer

Real objects do not perfectly absorb or emit all incident radiation, unlike an ideal blackbody.

Answer

The blackbody model is only applicable to objects in a vacuum.

Answer

The blackbody model does not work for objects at extremely low temperatures.

Answer

The blackbody model fails to consider the impact of the object's shape on radiation.

Question 6

Which of the following best describes a blackbody?

Accepted Answer

An object that absorbs and emits thermal radiation perfectly

Answer

An object that transmits all incoming thermal radiation

Answer

An object that reflects all incoming thermal radiation

Question 7

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

Accepted Answer

Wien's displacement law

Answer

Stefan-Boltzmann law

Answer

Kirchhoff's law

Answer

Planck's law

Question 8

What is the SI unit for the emissive power of a blackbody?

Accepted Answer

Watts per square meter

Answer

Joules per second

Answer

Watts per cubic meter

Question 9

Which of the following factors does NOT affect the emissivity of a blackbody?

Accepted Answer

Wavelength

Answer

Temperature

Answer

Surface texture

Answer

Material properties

Question 10

What is the relationship between the emissivity and absorptivity of a blackbody?

Accepted Answer

They are equal

Answer

They are inversely proportional

Answer

Emissivity is greater than absorptivity

Answer

Absorptivity is greater than emissivity

Question 11

Which of the following applications utilizes the principles of blackbody radiation?

Accepted Answer

Infrared cameras

Answer

Wind turbines

Answer

Solar panels

Answer

Hydroelectric generators

Question 12

What is the significance of Planck's law in blackbody radiation?

Accepted Answer

It provides the spectral distribution of emitted radiation

Answer

It predicts the wavelength of peak emission

Answer

It determines the emissive power

Question 13

Which of the following is a key difference between blackbody radiation and real-world emitters?

Accepted Answer

Real-world emitters have a spectral distribution that deviates from Planck's law

Answer

Real-world emitters emit radiation at shorter wavelengths

Answer

Real-world emitters have higher emissivities

Question 14

What is the impact of temperature on the emissive power of a blackbody?

Accepted Answer

It increases rapidly with temperature

Answer

It decreases exponentially with temperature

Answer

It remains constant over a wide temperature range

Question 15

Which of the following is NOT a consequence of Wien's displacement law?

Accepted Answer

Hotter objects peak at longer wavelengths

Answer

The wavelength of peak emission is inversely proportional to temperature

Answer

The sun's peak emission is in the visible spectrum

Answer

Stars appear different colors due to their varying temperatures

Question 16

A blackbody is defined as an object that:

Accepted Answer

Absorbs all incident radiation and emits radiation at a rate determined solely by its temperature.

Answer

Transmits all incident radiation.

Answer

Reflects all incident radiation.

Question 17

Planck's law describes the spectral radiance of a blackbody as a function of:

Accepted Answer

Wavelength and temperature.

Answer

Wavelength and surface area.

Answer

Temperature and emissivity.

Answer

Surface area and emissivity.

Question 18

Which of the following statements is TRUE about Wien's displacement law?

Accepted Answer

The wavelength at which a blackbody emits its maximum radiation is inversely proportional to its temperature.

Answer

The total energy emitted by a blackbody is directly proportional to its temperature.

Question 19

The Stefan-Boltzmann law states that the total energy radiated per unit area by a blackbody is proportional to:

Accepted Answer

The fourth power of its absolute temperature.

Answer

The cube of its absolute temperature.

Answer

The square of its absolute temperature.

Answer

Its absolute temperature.

Question 20

A blackbody at 1000 K emits a maximum radiation at a wavelength of approximately:

Accepted Answer

2.898 μm

Answer

1.45 μm

Answer

11.592 μm

Answer

5.796 μm

Question 21

Two blackbodies, one at 500 K and the other at 1000 K, are placed in a vacuum. Which blackbody emits more radiation per unit area?

Accepted Answer

The blackbody at 1000 K.

Answer

Both emit the same amount of radiation.

Answer

The blackbody at 500 K.

Question 22

A greybody is an object that:

Accepted Answer

Absorbs and emits radiation at a rate less than a blackbody.

Answer

Absorbs all incident radiation and emits radiation at a rate determined solely by its temperature.

Answer

Reflects all incident radiation.

Question 23

The emissivity of a surface is defined as:

Accepted Answer

The ratio of the radiant exitance of the surface to the radiant exitance of a blackbody at the same temperature.

Answer

The ratio of the absorbed radiation to the incident radiation.

Question 24

A real object, unlike a blackbody, will have an emissivity value that is:

Accepted Answer

Less than 1.

Answer

Greater than 1.

Answer

Dependent on the wavelength of radiation.

Answer

Equal to 1.

Question 25

Which of the following applications relies heavily on the principles of blackbody radiation?

Accepted Answer

Thermal imaging.

Answer

Conduction heat transfer.

Answer

Convection heat transfer.

Answer

Refrigeration.

Question 26

A blackbody is defined as an object that:

Accepted Answer

Absorbs all incident radiation and emits radiation at all wavelengths.

Answer

Reflects all incident radiation.

Answer

Transmits all incident radiation.

Question 27

According to Planck's Law, the spectral radiance of a blackbody is:

Accepted Answer

Dependent on both temperature and wavelength.

Answer

Linearly proportional to temperature.

Answer

Independent of temperature.

Answer

Independent of wavelength.

Question 28

The Stefan-Boltzmann Law states that the total energy radiated by a blackbody is:

Accepted Answer

Proportional to the fourth power of its absolute temperature.

Answer

Inversely proportional to its absolute temperature.

Answer

Proportional to its absolute temperature.

Question 29

Wien's Displacement Law describes the relationship between:

Accepted Answer

The wavelength of peak emission and the temperature of a blackbody.

Answer

The total energy radiated and the temperature of a blackbody.

Answer

The spectral radiance and the wavelength of a blackbody.

Question 30

A furnace operating at 1000 K emits maximum radiation at a wavelength of approximately:

Accepted Answer

2.898 µm

Answer

5.796 µm

Answer

11.592 µm

Answer

1.45 µm

Question 31

A blackbody at 500 K has a total energy radiated per unit area of:

Accepted Answer

3.55 x 10^5 W/m²

Answer

7.10 x 10^5 W/m²

Answer

1.78 x 10^5 W/m²

Answer

1.42 x 10^6 W/m²

Question 32

Which of the following surfaces is most likely to behave as a blackbody?

Accepted Answer

A cavity with a small opening.

Answer

A white painted surface.

Answer

A polished metal surface.

Answer

A transparent glass pane.

Question 33

The concept of blackbody radiation is fundamental to understanding:

Accepted Answer

Heat transfer by radiation.

Answer

Heat transfer by conduction.

Answer

Fluid mechanics.

Answer

Heat transfer by convection.

Question 34

What is the primary reason why the Sun's radiation is not considered a perfect blackbody radiation?

Accepted Answer

The Sun has a non-uniform temperature distribution.

Answer

The Sun emits radiation at specific wavelengths.

Answer

The Sun's atmosphere absorbs some of its radiation.

Question 35

How does the blackbody radiation spectrum change as the temperature increases?

Accepted Answer

The peak wavelength shifts towards shorter wavelengths and the total radiation intensity increases.

Answer

The peak wavelength shifts towards longer wavelengths and the total radiation intensity increases.

Answer

The peak wavelength shifts towards shorter wavelengths and the total radiation intensity decreases.