Window glass is transparent whereas wood is opaque. In the context of physics, a perfectly transparent object allows light rays to pass through with no loss of energy. A perfectly opaque object absorbs 100% of any light energy and completely stops light rays. Transparency and opacity depend on the material of the medium and also on its shape and surface characteristics. Even glass can be opaque when ground up as a powder. Read the text aloud
Transparent, translucent, and opaque materials
Many bathroom windows let in light but you cannot see an image through them. Frosted windows are translucent, which means that light rays pass through but their direction is scattered so the information (images) gets blurred or is completely eliminated. Transparent materials can be made translucent by changing the surface texture. Read the text aloud
Many objects may display all three properties—transparency, translucency, and opacity—to various degrees. The diagram at right shows an example. The optical properties depend on the application. Optical glass for eyeglass lenses must be nearly 100% transparent with 0% opacity (although a darkened coating may be applied to the surface to turn them into sunglasses). Read the text aloud Images simulating varying amounts of transparency, translucency, and opacity
A substance that is transparent to visible light may not be transparent to other wavelengths of light. For example, sunglasses may be 50% transparent to visible light yet only be 0.1% transparent to ultraviolet light (99.9% opaque). Earth’s atmosphere is transparent to visible light but partially opaque to infrared light. This results in the “greenhouse effect” in which solar energy arrives as visible light but heat energy cannot escape as infrared light. Read the text aloud Show Transparency and electromagnetic waves
Are tinted windows on cars partially translucent or partially opaque? Show

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