Question 1

Carbon dioxide and water molecules in the atmosphere will absorb:
A) infrared light.
B) visible light.
C) ultraviolet light.
D) radio waves.

Accepted Answer

Carbon dioxide and water molecules in the atmosphere are known as greenhouse gases because they absorb and emit infrared radiation, which is a type of electromagnetic radiation with longer wavelengths than visible light. This process traps heat in the atmosphere and contributes to the warming of the planet, known as the greenhouse effect. Therefore, the correct answer is A) infrared light.

Question 2

In winter, light-colored clothes will keep you warmer than dark-colored clothes if:
A) you are warmer than your surroundings.
B) you are at the same temperature as your surroundings.
C) you are cooler than your surroundings.
D) you are standing in sunlight.

Accepted Answer

Light-colored clothes reflect more sunlight and absorb less heat, which can keep you warmer than dark-colored clothes if you are warmer than your surroundings. Dark-colored clothes absorb more sunlight and retain more heat, making them better for keeping you cool in hot weather.

Question 3

An object at 27$\degree$C has its temperature increased to 47$\degree$C. The power then radiated by this object increases by how many percent?
A) 3.3
B) 14
C) 29
D) 253

Accepted Answer

The answer of An object at 27$\degree$C has its temperature...

Question 4

The emissivity of an ideal reflector has which of the following values?
A) 0
B) 1
C) 100
D) infinity

Accepted Answer

An ideal reflector reflects all radiation incident upon it, so it does not emit any radiation. Therefore, its emissivity value is 0.

Question 5

The surfaces of a Dewar flask are silvered for the purpose of minimizing heat transfer by what process?
A) conduction
B) radiation
C) convection
D) vaporization

Accepted Answer

The silvered surface reflects  radiation and helps to minimize heat transfer by radiation. Conduction and convection can still occur through any non-silvered surfaces, but silvering reduces the heat exchange by radiation, which is the primary mode of heat transfer in a vacuum flask. Vaporization is not a relevant process in this context.

Question 6

How does the heat energy from the Sun reach us through the vacuum of space?
A) conduction
B) radiation
C) convection
D) none of the above choices are valid

Accepted Answer

The heat energy from the Sun reaches us through the vacuum of space through radiation. Radiation is the transfer of energy through electromagnetic waves, which can travel through a vacuum. It does not require a medium to transfer heat energy.

Question 7

If the surface temperature of the Earth is  and that of the Sun is 6000 K, assuming the same emissivities, what is the ratio of the energy radiated per square meter of the Earth to that of the Sun?
A) 0.48
B) 
C) 
D)

Accepted Answer

The answer of If the surface temperature of the Earth...

Question 8

Which type of heating causes sunburn?
A) conduction
B) convection
C) radiation
D) all of the above

Accepted Answer

Sunburn is caused by radiation, specifically the ultraviolet (UV) radiation from the sun. Conduction and convection are forms of heat transfer through direct physical contact or movement of heated air or liquids, but they do not directly cause sunburn.

Question 9

What temperature increase is necessary to increase the power radiated from an object by a factor of 16?
A) 8 K
B) 2 K
C) 100%
D) about 68%

Accepted Answer

The answer of What temperature increase is necessary to increase...

Question 10

The surface of the Sun has a temperature of about 5800 K. If the radius of the Sun is 7*10⁸ m, determine the power output of the sun. (Take e = 1, and $\sigma$ = 5.67 *10^-⁸ W/m²·K⁴). A) 3.95 * 10²⁶ W B) 5.17 * 10²⁷ W C) 9.62 * 10²⁸ W D) 6.96 * 10³⁰ W

Accepted Answer

The power output of the sun is given by the Stefan-Boltzmann law:$$P = \sigma A T^4$$where:* P is the power output in watts* σ is the Stefan-Boltzmann constant (5.67 x 10^-8 W/m^2 K^4)* A is the surface area of the sun in square meters* T is the surface temperature of the sun in KelvinThe surface area of the sun is:$$A = 4\pi r^2$$where:* r is the radius of the sun in metersSubstituting the given values into the equations, we get:$$P = (5.67 x 10^-8 W/m^2 K^4) (4\pi (7 x 10^8 m)^2) (5800 K)^4$$$$P = 3.95 x 10^26 W$$Therefore, the power output of the sun is 3.95 x 10^26 W.

Question 11

The filament temperature of a light bulb is 2000 K when the bulb delivers 50 W of power. If its emissivity remains constant, what power is delivered when the filament temperature is 2500 K?
A) 122 W
B) 62 W
C) 98 W
D) 50 W

Accepted Answer

The answer of The filament temperature of a light bulb...

Question 12

At high noon, the Sun delivers 900 W to each square meter of a blacktop road. What is the equilibrium temperature of the asphalt, assuming its emissivity e = 1? ($\sigma$ = 5.67*10^-⁸ W/m²*K⁴) . A) 75$\degree$C B) 82$\degree$C C) 91$\degree$C D) 99$\degree$C

Accepted Answer

The answer of At high noon, the Sun delivers 900...

Question 13

The Sun is a slightly variable star. What if the surface temperature of the Sun were to increase from 6000 K to 6100 K, what would be the increase in total power radiated assuming no other changes such as radius or emissivity?
A) 1.6%
B) 6.8%
C) 3.4%
D) 14%

Accepted Answer

The total power radiated by a star like the Sun can be calculated using the Stefan-Boltzmann law, which states that the power radiated per unit area is proportional to the fourth power of the temperature (P ∝ T^4). If the temperature increases from 6000 K to 6100 K, the increase in power radiated can be calculated as (6100/6000)^4 - 1. This results in approximately a 6.8% increase in the total power radiated.

Question 14

In a greenhouse, electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated. What happens to this reradiated electromagnetic radiation from within the greenhouse?
A) 100% returns to the atmosphere.
B) It's partially blocked by glass.
C) It's transformed into ultraviolet upon striking the glass.
D) It's reflected as visible light upon striking the glass.

Accepted Answer

The reradiated electromagnetic radiation from within the greenhouse is partially blocked by glass, which traps the heat within the greenhouse and helps to regulate the temperature.

Question 15

The tungsten filament of a light bulb has an operating temperature of about 2100 K. If the emitting area of the filament is 0.80 cm², and its emissivity is 0.68, what is the power output of the light bulb? ($\sigma$ = 5.67 *10^-⁸ W/m²·K⁴) A) 100 W B) 75 W C) 60 W D) 40 W

Accepted Answer

The power output can be calculated using the Stefan-Boltzmann law: P = εσAT⁴. Substituting the given values: ε = 0.68, σ = 5.67 × 10⁻⁸ W/m²·K⁴, A = 0.80 cm² = 0.00008 m², and T = 2100 K, we find P ≈ 60 W.

Quiz 14: Temperature and Heat

Carbon dioxide and water molecules in the atmosphere will absorb:

In winter, light-colored clothes will keep you warmer than dark-colored clothes if:

An object at 27 $\degree$ C has its temperature increased to 47 $\degree$ C. The power then radiated by this object increases by how many percent?

The emissivity of an ideal reflector has which of the following values?

The surfaces of a Dewar flask are silvered for the purpose of minimizing heat transfer by what process?

How does the heat energy from the Sun reach us through the vacuum of space?

If the surface temperature of the Earth is and that of the Sun is 6000 K, assuming the same emissivities, what is the ratio of the energy radiated per square meter of the Earth to that of the Sun?

Which type of heating causes sunburn?

What temperature increase is necessary to increase the power radiated from an object by a factor of 16?

The surface of the Sun has a temperature of about 5800 K. If the radius of the Sun is 710⁸ m, determine the power output of the sun. (Take e = 1, and $\sigma$ = 5.67 10^-⁸ W/m²·K⁴) .

The filament temperature of a light bulb is 2000 K when the bulb delivers 50 W of power. If its emissivity remains constant, what power is delivered when the filament temperature is 2500 K?

At high noon, the Sun delivers 900 W to each square meter of a blacktop road. What is the equilibrium temperature of the asphalt, assuming its emissivity e = 1? ( $\sigma$ = 5.6710^-⁸ W/m²K⁴) .

The Sun is a slightly variable star. What if the surface temperature of the Sun were to increase from 6000 K to 6100 K, what would be the increase in total power radiated assuming no other changes such as radius or emissivity?

In a greenhouse, electromagnetic energy in the form of visible light enters the glass panes and is absorbed and then reradiated. What happens to this reradiated electromagnetic radiation from within the greenhouse?

The tungsten filament of a light bulb has an operating temperature of about 2100 K. If the emitting area of the filament is 0.80 cm², and its emissivity is 0.68, what is the power output of the light bulb? ( $\sigma$ = 5.67 *10^-⁸ W/m²·K⁴)