Wave Interactions

Science, Grade 6


Table Of Contents: Wave Interactions

1. Transmission of Light
Why can you see through glass but not wood? Why do you see a blurry image through frosted glass? When light strikes the surface of any material, it can be reflected, transmitted, or absorbed. Glass allows most of the light to be transmitted and allows us to see through the glass. These kinds of materials are called transparent. Frosted glass allows light to be transmitted, however the rays are bent in many directions, causing a blurry image. Materials like this are called translucent. Opaque materials such as wood absorb the light so you cannot see through it. Opaque materials absorb or reflect light but do not transmit light.
2. Color for Opaque Objects
Why does an apple look red and a leaf green? When white light strikes the surface of the apple, only red light is reflected. All the other colors are absorbed by the apple. Your eyes only see the red light, so you say the apple is red. The leaf appears green because only green light is reflected from the leaf. White objects reflect all the colors of light which your eye interprets as white. Black objects absorb all the colors of light. This is why a black t-shirt gets hot in the Sun. The black material absorbs all the energy of the light. The energy from the light is converted to heat.
3. Color with Transparent or Translucent Objects
The color of a transparent or translucent object is determined by the color of light it transmits. A green filter will only allow green light to pass through while all the other colors are absorbed. A color filter is a transparent or translucent material such as the lenses of your sunglasses. An object can appear to be a different color than it actually is if it is viewed through a color filter. For example, a red apple normally appears red because it reflects red light. However, when this red apple is viewed through a green filter, the red light is absorbed and the red apple will now appear black. Its green leaf will still look green because the green light can pass through the lens.
4. Combining Colors of Light
Primary colors of light – blue, green and red combine to produce white light. Secondary colors of light are produced by combining two different primary colors known as color addition. For example, red and blue combine to produce magenta, red and green produce yellow, while green and blue produce cyan. The colors that you see on your television set are produced by color addition.
5. Colors of Pigments
The primary colors of pigments are magenta, yellow, and cyan. Any of these two primary pigments can be combined to produce a secondary pigment color. For example, magenta and cyan when combined make blue. However, when the three primary colors are combined in equal amounts, all the colors of light are absorbed resulting in a black pigment. The colors you see on a printed image are produced by combining different color pigments.