Blackbody Radiation Questions: Quiz!

1. If the only change you make is to decrease the temperature of an object, the total amount of power emitted decreases in all cases.

True

False

When the temperature of an object decreases, the average kinetic energy of its particles also decreases. As a result, the object emits less thermal radiation, which is a form of electromagnetic radiation and represents the power emitted by the object. Therefore, decreasing the temperature of an object leads to a decrease in the total amount of power emitted in all cases.

Explanation

When the temperature of an object decreases, the average kinetic energy of its particles also decreases. As a result, the object emits less thermal radiation, which is a form of electromagnetic radiation and represents the power emitted by the object. Therefore, decreasing the temperature of an object leads to a decrease in the total amount of power emitted in all cases.

2. If we observe a star's spectrum and find that the peak power occurs at the border between blue and ultraviolet light, what is the surface temperature of the star? (in degrees C)

200

2000

3000

7000

The peak power of a star's spectrum occurring at the border between blue and ultraviolet light indicates that the star has a high surface temperature. The higher the temperature, the bluer the light emitted by the star. Therefore, the surface temperature of the star is likely to be around 7000 degrees Celsius.

Explanation

The peak power of a star's spectrum occurring at the border between blue and ultraviolet light indicates that the star has a high surface temperature. The higher the temperature, the bluer the light emitted by the star. Therefore, the surface temperature of the star is likely to be around 7000 degrees Celsius.

3. Is the most powerful (peak) wavelength emitted from a light bulb in the visible light range?

Yes

No

It's on the border

The most powerful (peak) wavelength emitted from a light bulb is not in the visible light range.

Explanation

The most powerful (peak) wavelength emitted from a light bulb is not in the visible light range.

4. Light bulbs operate at 2500 degrees C. What is the wavelength at which the most power is emitted for a light bulb operating at 2500 C?

200 nm

600 nm

1200 nm

6000 nm

The wavelength at which the most power is emitted for a light bulb operating at 2500 degrees C is 1200 nm. This is because as the temperature of an object increases, the peak wavelength of its emitted radiation shifts towards shorter wavelengths. Therefore, at a high temperature of 2500 degrees C, the light bulb emits the most power at a wavelength of 1200 nm.

Explanation

The wavelength at which the most power is emitted for a light bulb operating at 2500 degrees C is 1200 nm. This is because as the temperature of an object increases, the peak wavelength of its emitted radiation shifts towards shorter wavelengths. Therefore, at a high temperature of 2500 degrees C, the light bulb emits the most power at a wavelength of 1200 nm.

5. The temperature of stars in the universe varies with the type of star and the age of the star, among other things. By looking at the shape of the spectrum of light emitted by a star, we can tell something about its average surface temperature. If we observe a star's spectrum and find that the peak power occurs at the border between red and infrared light, what is the approximate surface temperature of the star? (in degrees C)

200

2000

4000

8000

By observing the spectrum of light emitted by a star, we can determine its average surface temperature. If the peak power occurs at the border between red and infrared light, it indicates that the star has a surface temperature of approximately 4000 degrees Celsius.

Explanation

By observing the spectrum of light emitted by a star, we can determine its average surface temperature. If the peak power occurs at the border between red and infrared light, it indicates that the star has a surface temperature of approximately 4000 degrees Celsius.

6. Investigate how the observed spectrum responds to changing temperature. Note you are only able to change temperature here but should consider how the spectrum (power vs. color) would change if you varied other characteristics of the object. If the only change you make is to decrease the temperature of an object, the amount of power emitted at 1000 nm will increase in some cases.

True

False

If the only change made is to decrease the temperature of an object, the amount of power emitted at 1000 nm will not increase. The statement in the question suggests that the observed spectrum responds to changing temperature, but it does not specify how. Therefore, it is not accurate to conclude that decreasing the temperature will lead to an increase in power emitted at 1000 nm.

Explanation

If the only change made is to decrease the temperature of an object, the amount of power emitted at 1000 nm will not increase. The statement in the question suggests that the observed spectrum responds to changing temperature, but it does not specify how. Therefore, it is not accurate to conclude that decreasing the temperature will lead to an increase in power emitted at 1000 nm.

7. Evolution is about the most efficient species for the area that will survive, so most life on the earth sees in the same visual spectrum. If life was to develop in a solar system with a red giant (3000 C) instead of a yellow star (5700 C)

There would be no difference in the visual light they would see.

They would see more into the ultraviolet.

They would see more in the infrared.

None of the above

In a solar system with a red giant instead of a yellow star, the temperature of the star would be lower. Red giants emit more infrared light compared to yellow stars, which emit more visible light. Therefore, if life were to develop in such a solar system, the organisms would likely have evolved to see more in the infrared spectrum to adapt to the predominant light source.

Explanation

In a solar system with a red giant instead of a yellow star, the temperature of the star would be lower. Red giants emit more infrared light compared to yellow stars, which emit more visible light. Therefore, if life were to develop in such a solar system, the organisms would likely have evolved to see more in the infrared spectrum to adapt to the predominant light source.

8. Use the Spectrum Simulation to investigate changes in the amount of light at visible wavelengths due to this change in temperature from 2500 C to 2000 C. What is the approximate ratio between the powers emitted at 500 nm at 2000 degrees C to that at 2500 degrees C, that is, the power emitted at 500 nm at 2000 degrees C divided by the amount of power at 500 nm at degrees 2500 C?

2 to 1

5 to 1

11 to 1

100 to 1

The question asks for the approximate ratio between the powers emitted at 500 nm at 2000 degrees C to that at 2500 degrees C. The answer is 11 to 1, indicating that the power emitted at 500 nm at 2000 degrees C is approximately 11 times greater than the power emitted at 500 nm at 2500 degrees C. This suggests that as the temperature decreases from 2500 degrees C to 2000 degrees C, the amount of light emitted at 500 nm also decreases significantly.

Explanation

The question asks for the approximate ratio between the powers emitted at 500 nm at 2000 degrees C to that at 2500 degrees C. The answer is 11 to 1, indicating that the power emitted at 500 nm at 2000 degrees C is approximately 11 times greater than the power emitted at 500 nm at 2500 degrees C. This suggests that as the temperature decreases from 2500 degrees C to 2000 degrees C, the amount of light emitted at 500 nm also decreases significantly.

9. What is the approximate peak wavelength for a bulb operating at 2000 degrees C?

200 nm

400 nm

800 nm

1200 nm

1400 nm

The approximate peak wavelength for a bulb operating at 2000 degrees C is 1400 nm. This is because as the temperature of an object increases, the peak wavelength of its emitted radiation also increases. This relationship is described by Wien's displacement law, which states that the peak wavelength is inversely proportional to the temperature. Therefore, a higher temperature like 2000 degrees C corresponds to a longer peak wavelength of 1400 nm.

Explanation

The approximate peak wavelength for a bulb operating at 2000 degrees C is 1400 nm. This is because as the temperature of an object increases, the peak wavelength of its emitted radiation also increases. This relationship is described by Wien's displacement law, which states that the peak wavelength is inversely proportional to the temperature. Therefore, a higher temperature like 2000 degrees C corresponds to a longer peak wavelength of 1400 nm.

10. At what temperature is the most efficient temperature, in Celsius for visible light?

1000

2250

3500

4500

5500

The most efficient temperature for visible light is 5500 degrees Celsius. This is because at this temperature, objects emit the highest amount of visible light. As the temperature increases, the intensity of visible light emitted also increases. Therefore, 5500 degrees Celsius is the optimal temperature for maximizing the efficiency of visible light emission.

Explanation

The most efficient temperature for visible light is 5500 degrees Celsius. This is because at this temperature, objects emit the highest amount of visible light. As the temperature increases, the intensity of visible light emitted also increases. Therefore, 5500 degrees Celsius is the optimal temperature for maximizing the efficiency of visible light emission.