Glossary

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heat - the transfer of thermal energy from one substance to another due to a difference in temperature.

heat engine - a device that turns heat energy into mechanical work.

heat pump - pumps heat from one location to another. A heat pump can remove heat from the inside of a building and pump it outside (similar to an air conditioner), or it can take heat from outside and pump it indoors.

hypermetropia - (farsightedness, sometimes called hyperopia) the inability of the eye to focus clearly on near objects. The lens is too flat or the eyeball is too short resulting in the image forming behind the retina.

illuminance - the amount of light on a surface area measured in lux

incandescent body - a body that emits light after being heated (eg. a light bulb).

incident ray - a ray approaching a surface.

indirect lighting - light that reflects off one or more rough surfaces resulting in few or soft shadows. Indirect lighting is sometimes called soft lighting or diffuse.

infrared light - part of the electromagnetic spectrum between the red side of visible light and microwaves. Infrared cannot be detected by the human eye.

infrasonic frequencies - frequencies below 20 Hz, the lowest frequencies detected by most humans.

iris - the colored ring of tissue behind the cornea and in front of the lens. The iris regulates the amount of light passing by changing the size of the pupil.

interference - two or more waves acting simultaneously on the same particles of a medium.

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