Why Doesn't Visible Light Cook Us? Exploring the Energy Differences Between Visible and Infrared Light

Introduction

When considering the heating capabilities of light, it's natural to ask, 'if infrared light is hot then why doesn’t visible light cook us?' This question delves into the fundamental differences between these two forms of light and their respective energy levels.

The Historical Use of Infrared and Visible Light in Cooking

Before the widespread adoption of microwave ovens and other modern cooking technologies, infrared heaters and visible light sources were commonly used to quickly heat foods. For instance, infrared heaters were used to warm up heated containers of soup or pre-cooked foods like burgers and hotdogs. Even novel solutions such as canned soup machines with warm cans became popular in transport facilities and waiting areas across the country.

Understanding the Energy Differences

When it comes to cooking, visible light sources don't measure up to their infrared counterparts. Thermal sources, which are the cheapest and easiest to use, generate far more infrared than visible light. For example, cooking over a fire generates a large amount of infrared radiation with a relatively small amount of visible light, such as in a barbecue. Higher intensity sources like blowtorches or acetylene flames can also be used for cooking, but this often requires a change in cooking methods.

Non-Thermal Light Sources

Non-thermal light sources, such as lasers, can generate only visible light without infrared. However, these sources are often much more expensive. A high-powered laser might cost tens of thousands of dollars, while a simple charcoal fire can produce the necessary heat for cooking for just a few dollars. From an economic standpoint, thermally-generated infrared light is far more cost-effective than visible light.

The Nature of Infrared and Visible Light

Infrared light, often associated with heat, is the light given off by objects at common temperatures. An infrared camera can detect the heat emitted by a person, for example, while steel heated to a high enough temperature will give off visible light. A source that's even hotter might eventually emit x-rays. The difference between infrared and visible light lies in their wavelengths and the energy carried by the individual photons.

Energy and Intensity

The wavelength of light is directly related to the energy carried by the individual photons. However, this doesn't determine the intensity of the light. High-intensity visible light, such as that from powerful LED lamps, can be quite hot, while low-intensity infrared radiation, such as that from infrared remote controls, is barely noticeable. Another factor in the perceived heat of light is absorption. Infrared light is often better absorbed by various materials than visible light, which can make it feel hotter.

Conclusion

The difference in the energy levels between visible and infrared light explains why visible light doesn't cook us like infrared does. While visible light may carry more energy in terms of photon energy, its lower intensity and poor absorption by materials in comparison to infrared light means it is less effective at cooking. Understanding these differences helps in appreciating why infrared technology is preferred in many cooking and heating applications.