Contact Lenses and Reflection

I didn’t really experience anything exciting that was physics-related this week; however, when I was putting in my contacts this morning, I remembered that we are learning about lenses. I always wanted to know how contact lenses worked ever since I got them because my vision improved dramatically when I got contacts. I’m nearsighted, which means that my eyes can’t focus on far away objects because the light rays converge in front of the retinas in my eyes. Therefore, I need diverging lenses in order to help me see faraway things because diverging lenses make the light rays diverge a little more so that they can converge farther away, at the retinas. When I was looking at my contacts, I also realized that they are fatter at the edges than at the center, just like our textbook says about diverging lenses for nearsightedness. When I was taking the picture of my contacts for this blog, I also realized that I was in front of a plane mirror, and since we are also learning about reflection, I decided to incorporate the image of my contact lenses in the picture.

A Convection Oven

I was using a convection oven to cook French bread pizza for lunch today, and it occurred to me that I never knew how it works (besides that it cooks my food faster than a regular oven). What are the physics behind it that power it and heat up my food? I decided to look that up and find out for myself. I found out that “convection” is the movement of molecules, and the process of convective heat transfer occurs through diffusion, the random movement of particles. Heat transfer works by the transition of thermal energy, and we learned that heat always flows from the hotter object to the colder one. Forced convection is the heat transfer of a fluid that is not induced by a natural heating force. This is the type of convection that powers a convection oven. In a convection oven, a fan is turned on and spins quickly so that the heat it produces is used to heat up the food. In this case, the heat from the fan is transferred to the food and heats it up because the food is colder than the fan. Who knew you could learn so much about physics by just making your lunch.