Question

Which of the following does not radiate heat? a) ice cube b) liquid nitrogen c) liquid helium d) a device at \(T=0.010 \mathrm{~K}\) e) all of the above f) none of the above

Short answer

Short Answer: e) all of the above.

Step-by-step solution

- Understanding heat radiation

Heat radiation occurs when an object transfers thermal energy to its surroundings in the form of invisible electromagnetic waves called infrared radiation. All objects above absolute zero temperature (\(0 \mathrm{~K}\)) emit thermal radiation due to the vibration and movement of their constituent particles. The amount of heat an object radiates is directly proportional to the amount of vibrational energy its particles possess relative to the surrounding temperature.

- Analyzing given options

Let's examine each option and determine its ability to radiate heat. a) ice cube: An ice cube is a solid object which has a temperature above absolute zero. Therefore, it will radiate heat. b) liquid nitrogen: Liquid nitrogen has a temperature of about \(77 \mathrm{~K}\). Since it is above absolute zero, it will radiate heat. c) liquid helium: Liquid helium has a temperature of approximately \(4 \mathrm{~K}\). Even though its temperature is very low, it is still above absolute zero. Therefore, it will radiate heat. d) a device at \(T=0.010 \mathrm{~K}\): This device has a temperature of \(0.010 \mathrm{~K}\), only slightly above absolute zero. While at such a low temperature its heat radiation would be extremely small, since it is above absolute zero, it will still radiate some amount of heat.

- Identifying the correct option

Based on our analysis of the given options, all of them emit some amount of heat due to their temperatures being above absolute zero. Hence, the correct answer is: e) all of the above

Key concepts

Thermal Energy

Thermal energy is a form of energy that derives from the temperature of matter. It's the energy that comes from the kinetic energy—the movement—of atoms and molecules within a substance.

Every substance with a temperature above absolute zero has thermal energy due to the motion of its particles. When the particles are faster, meaning the object has a higher temperature, there's more thermal energy.

Understanding Thermal Energy in Everyday Objects

Consider an ice cube, which feels cold to the touch. Despite its low temperature, it still has thermal energy because its molecules are in constant motion, though they move much slower compared to those in warmer objects.

Likewise, substances like liquid nitrogen and liquid helium have relatively low temperatures but they too possess thermal energy. In the realm of thermodynamics, it's crucial to recognize that 'cold' simply means 'less heat', but not the absence of heat or thermal energy.

Infrared Radiation

Infrared radiation is a type of electromagnetic radiation that falls just beyond the visible spectrum, meaning we can't see it with the naked eye. However, we can often feel it as warmth. Objects release this energy in the form of infrared waves, based on their temperature.

The Role of Infrared in Heat Transfer

Even at room temperature, objects emit infrared radiation which is a natural consequence of their thermal energy. The sun is a potent source of infrared radiation, which warms the Earth every day. But even a seemingly cold object, like an ice cube, emits infrared radiation due to the minuscule movements of its particles.

It's this infrared radiation that allows us to use thermal imaging cameras to see the heat of an object - whether it's a living being or an inanimate object, as long as its temperature is above absolute zero, it will give off this type of radiation. The concept is vital in various applications, including weather forecasting, astronomy, and even medical diagnostics.

Absolute Zero Temperature

Absolute zero is the theoretical lowest possible temperature where the particles in a substance contain no thermal energy. In the Kelvin scale, this is 0 K, equivalent to -273.15 degrees Celsius or -459.67 degrees Fahrenheit.

Why Absolute Zero Is Significant

At absolute zero, it would be expected that all motion of particles would cease; however, due to quantum mechanical effects, particles still possess some zero-point energy - the lowest possible energy a quantum mechanical physical system may have.

Even objects that are incredibly cold, such as technology operating near absolute zero for scientific research, still emit a dim level of heat radiation. The idea of absolute zero is more than just a benchmark for temperature; it also has profound implications for the nature of energy and motion within physics. Understanding that no real system can actually reach absolute zero, and even if a substance is extremely cold, like the device mentioned in the exercise at 0.010 K, it will still emit an infinitesimal amount of radiation, reinforces the fact that purely 'cold' radiation does not exist in the physical world.