# Understanding Wavelength, Energy, & Temperature

• Alex48674
In summary, from quantum mechanics, the energy of a photon is given by E=hf, where h is a constant and f is the frequency of the wave. It can be seen that as space expands and the wavelength increases, the energy of the photon decreases. This is due to the relationship between energy and wavelength in quantum mechanics, as opposed to the classical relationship with amplitude.
Alex48674
I know that as space expands it cause light to force itself to increase its wavelength, but I can't seem to remember how it relates to a decrease in energy, and thus a decrease in temperature. I know that in this respect energy is related to wavelength as opposed to how it classically related to amplitude.

Thanks, I hope I've got that much right so far =]

From quantum mechanics, the energy of a photon is given by

$$E=hf$$

where h is a constant (Plancks constant) and f is the frequency of the wave. Using the basic wave equation

$$v=f\lambda$$

where $$\lambda$$ is the wavelength, and taking the velocity of light to be c we get

$$E=\frac{hc}{\lambda}$$

So, as the 'classical' wavelength increases, the energy of the photon decreases.

I hope that helps, let me know if I'm being too equationy!

Wallace said:
From quantum mechanics, the energy of a photon is given by

$$E=hf$$

where h is a constant (Plancks constant) and f is the frequency of the wave. Using the basic wave equation

$$v=f\lambda$$

where $$\lambda$$ is the wavelength, and taking the velocity of light to be c we get

$$E=\frac{hc}{\lambda}$$

So, as the 'classical' wavelength increases, the energy of the photon decreases.

I hope that helps, let me know if I'm being too equationy!

Perfect thanks =]

## 1. What is the relationship between wavelength, energy, and temperature?

Wavelength, energy, and temperature are all related to each other through the electromagnetic spectrum. As the wavelength of a wave decreases, the energy of the wave increases. This is known as the inverse relationship between wavelength and energy. Additionally, as the temperature of an object increases, the average energy of the molecules within the object also increases. Therefore, there is a direct relationship between temperature and energy.

## 2. How does wavelength affect the temperature of an object?

The wavelength of a wave does not directly affect the temperature of an object. However, the type of electromagnetic radiation that an object absorbs and emits is determined by its temperature. Objects with higher temperatures emit shorter wavelengths of radiation, such as visible light, while cooler objects emit longer wavelengths, such as infrared radiation.

## 3. What is the relationship between the color of an object and its temperature?

The color of an object is determined by the wavelengths of light it reflects. As an object's temperature increases, it emits shorter wavelengths of light, shifting the color towards the blue end of the visible spectrum. As the temperature decreases, the object emits longer wavelengths, making the color shift towards the red end of the spectrum.

## 4. How does the energy of a wave change as its wavelength changes?

The energy of a wave is directly proportional to its frequency and inversely proportional to its wavelength. As the wavelength decreases, the frequency increases, and therefore, the energy of the wave increases. This is why shorter wavelengths, such as gamma rays and X-rays, have higher energy than longer wavelengths, like radio waves.

## 5. How is the temperature of an object related to the energy it emits?

The temperature of an object is directly related to the energy it emits through radiation. As an object's temperature increases, the molecules within the object move faster, and therefore, emit more energy in the form of electromagnetic radiation. The type and amount of radiation emitted are determined by the temperature of the object, with hotter objects emitting more energy at shorter wavelengths.

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