Question 1

You begin with an object at a certain temperature,and you increase its temperature by an amount ∆T.For which one of the following values of ∆T will the final temperature of the object be LOWEST?

Accepted Answer

The final temperature of the object will be lowest when the increase in temperature is in degrees Fahrenheit because Fahrenheit has a smaller degree size than both Celsius and Kelvin. Therefore, a change of 10 degrees Fahrenheit is less than both a change of 10 degrees Celsius and a change of 10 Kelvins, resulting in a lower final temperature. Answers A and B are incorrect because they involve larger degree sizes and would result in a higher final temperature.

Question 2

A scientist measures the temperature change between freezing water and boiling water with a thermometer calibrated in the Kelvin or absolute scale.How many degrees Kelvin (K)will he measure?

Accepted Answer

The answer of A scientist measures the temperature change between...

Question 3

A scientist reports that his measurement of the temperature of the surface of a newly discovered planet is -20 K.What conclusion can you draw from this report?

Accepted Answer

The result is erroneous because the absolute temperature cannot be negative. The Kelvin scale of temperature, which is an absolute temperature scale, does not have negative values.

Question 4

Which of the following statements is TRUE if the star Betelgeuse has a lower surface temperature than the Sun? (Assume that IR means infrared radiation and UV means ultraviolet radiation.)

Accepted Answer

The answer of Which of the following statements is TRUE...

Question 5

We plot the intensity of the radiation emitted from an object at a certain temperature versus its wavelength.As we increase the temperature,the wavelength at which the spectrum peaks becomes shorter and shorter.This is an example of:

Accepted Answer

The phenomenon described is known as Wien's law, which states that as the temperature of an object increases, the wavelength at which the spectrum of its intensity peaks becomes shorter.

Question 6

The minimum temperature reached on the surface of Mars,-140°C,is represented on the absolute (Kelvin)temperature scale as:

Accepted Answer

To convert -140°C to Kelvin, add 273.15 to the Celsius temperature: -140 + 273.15 = 133.15 K, which rounds to 133 K. Kelvin temperatures cannot be negative.

Question 7

A change of one unit on which of the following temperature scales will result in the SMALLEST temperature change?

Accepted Answer

The answer of A change of one unit on which...

Question 8

The normal temperature of the melting point of water ice is:

Accepted Answer

The normal temperature of the melting point of water ice is 273 K or 0°C. This is because water freezes at 273 K and melts at the same temperature. Other choices are not correct as 293 K is the approximate room temperature, 0 K is the absolute zero temperature which is unattainable, and 100 K is the boiling point of water at standard pressure.

Question 9

The temperature at the top of the clouds on Jupiter is about 165 K.In degrees Celsius,this temperature is:

Accepted Answer

To convert Kelvin to Celsius, subtract 273 from the Kelvin temperature. 165 K - 273 = -108°C.

Question 10

The Kelvin scale measures:

Accepted Answer

The Kelvin scale measures temperature in Celsius-sized degrees above absolute zero, making it a thermodynamic temperature scale. Absolute zero is the point at which no more thermal energy can be removed from a system, theoretically the lowest possible temperature. Unlike Fahrenheit or Celsius, the Kelvin scale starts at this point, making its unit size the same as that of Celsius but without negative values.

Question 11

The star Vega has a higher surface temperature than the Sun.Then with IR indicating infrared and UV indicating ultraviolet,Vega emits _____ IR and _____ UV flux than the Sun.

Accepted Answer

Vega has a higher surface temperature than the Sun, so it emits more UV flux than the Sun. Also, Vega emits less IR flux than the Sun because it has a higher surface temperature.

Question 12

Cepheid variable stars pulsate regularly in size.During the contraction part of the cycle,when the star's temperature is increasing,the peak wavelength of the emitted radiation will:

Accepted Answer

According to Wien's Law, as the temperature of a star increases, the peak wavelength of the emitted radiation shifts to shorter wavelengths. Therefore, during contraction when the temperature increases, the peak wavelength shifts from the visible to the UV part of the spectrum.

Question 13

Which one of these temperatures is HOTTEST?

Accepted Answer

100°C is the hottest temperature among the given options, as it represents the boiling point of water at standard pressure. 
100 K is only -173°C, which is very cold. 
100°F is equivalent to approximately 37.8°C, which is roughly body temperature.

Question 14

The temperature of boiling water at ordinary air pressure on the absolute scale-Kelvin-is:

Accepted Answer

The boiling point of water on the Kelvin scale is 373 K. This is because the Kelvin scale is based on absolute zero, which is -273°C. Therefore, 0°C is equal to 273 K, and the boiling point of water at 100°C is equal to 373 K. A is incorrect because 273 K is equivalent to 0°C, which is the freezing point of water. B and C are also incorrect because they are too low to be the boiling point of water.

Question 15

The range of temperatures in the Kelvin (absolute)scale between the freezing point and boiling point of water is:

Accepted Answer

The freezing point of water is 273.15 K and the boiling point is 373.15 K, so the range is 373.15 K - 273.15 K = 100 K.

Question 16

On the absolute Kelvin temperature scale,the temperature of freezing water is about:

Accepted Answer

On the Kelvin temperature scale, the point at which water freezes is defined as 273.15 K. Therefore, the temperature of freezing water is approximately 273 K.

Question 17

A typical but very cool star might have a temperature of 3100° Celsius.On the Kelvin scale,this is about:

Accepted Answer

The Kelvin scale starts at absolute zero, which is -273.15°C. To convert Celsius to Kelvin, you simply add 273.15. Therefore, 3100 + 273.15 = 3373, making choice A the correct answer. Choice B is incorrect because 0 K is actually -273.15°C, not 32°C. Choice C is also incorrect because the scales are not the same; the Kelvin scale is based on absolute zero while the Celsius scale is based on the freezing and boiling points of water. Choice D is also incorrect as it does not match the correct conversion.

Question 18

The hot,dense gas existing on the Sun emits energy:

Accepted Answer

The hot, dense gas on the Sun emits energy at all wavelengths, with a peak at one specific wavelength (color). This is known as blackbody radiation and is described by Planck's law. The peak wavelength depends on the temperature of the gas, and for the Sun, it falls in the visible range, giving the Sun its yellow-white color.

Question 19

What is the MAIN reason that astronomers (and other scientists)almost always use the Kelvin (absolute)temperature scale rather than the Celsius or Fahrenheit scales?

Accepted Answer

The Kelvin scale has a physically meaningful absolute zero of temperature, which makes it more suitable for scientific calculations and comparisons than Celsius or Fahrenheit scales.

Question 20

If all stars are considered to be perfect blackbodies,then the following relationship should hold regarding the energy flux,or energy emitted per unit area,from stars.

Accepted Answer

According to the Stefan-Boltzmann law, the energy flux emitted per unit area (also known as the surface brightness) from a blackbody is proportional to the fourth power of its temperature. Therefore, all stars of the same temperature (regardless of their mass, composition, or size) should emit the same energy flux.

Quiz 3: Light and Telescopes