Grade 8 Science
#1 DUE _________
Practice CRT Instructional Materials
Read the technical passage below. Write your answers for the questions on a separate piece of paper. Be
sure to answer Part A, B and C.
Transparent, Translucent, Opaque
Adapted from: http://science.jrank.org/pages/1593/Color-Transparent-translucent-opaque.html
Substances like clear glass, water and air are commonly referred to as transparent. When light hits a transparent material,
almost all of it passes directly through the object. Glass, for example, is transparent to all visible light, and even some
ultraviolet radiation (UVA rays – NOT the tan-inducing UVB ones…)!
Materials like frosted glass and some plastics are called translucent. When light strikes a translucent material, only some
of the light passes through. The rest of the light is reflected off of the surface, or absorbed into the material itself. The
light that makes it into the translucent object does not actually pass directly through the material. It changes direction
many times, and scatters as it passes through. Because of this, we cannot see clearly through these objects, and things that
we see on the other side of a translucent object appear “fuzzy and unclear”. Because translucent objects are part-way
transparent, some ultraviolet light rays can pass through them. This explains why a person behind a translucent object can
still get a sunburn on a sunny day.
Most materials are not clear or fuzzy, but are considered opaque. In opaque objects, none of the light that hits its surface
passes through. The light is either reflected by the object, or absorbed into the substance and converted into heat energy.
Materials such as wood, metals and stone are opaque to visible light. We can observe that light is being blocked anytime
we see a shadow!
Each picture below shows a ray of light interacting with a different surface. One surface is a shiny metal,
one surface is clear plastic, and one surface is painted black.
A. Identify which surface is most likely made of a shiny metal. Explain your answer.
B. Identify which surface is most likely made of clear plastic. Explain your answer.
C. Identify which surface is most likely painted black. Explain your answer.
Grade 8 Science
#2 DUE _________
Practice CRT Instructional Materials
Read the technical passage below. Write your answers for the questions on a separate piece of paper. Be
sure to answer Part A, B and C.
Electromagnetic Waves of the EM Spectrum
Adapted from: http://www.physicsclassroom.com/class/light/u12l2a.cfm
Unlike mechanical waves, Electromagnetic waves are waves that do not require a medium to travel through.
Instead, Electromagnetic waves, or “EM” waves, travel best through the vacuum of outer space. In a vacuum, EM waves
travel at an astonishing speed of 330 million m/s. They may slow down or even stop though if they come into contact
with a medium. X-rays and gamma rays are blocked out by the Earth’s atmosphere and magnetosphere, while EM waves
like radio waves, visible light, as well as some infrared and ultraviolet rays can pass through the gasses that make up
Earth’s atmosphere.
EM waves are given off by the sun and other stars, and transfer energy throughout the universe. These waves
exist with an enormous range of frequencies, and the continuous range of frequencies is known as the Electromagnetic
Spectrum. The spectrum is often broken into specific regions, each of varying frequency and wavelength. The diagram
below depicts the electromagnetic spectrum and its various regions. Two very narrow regions within the spectrum are the
visible light region and the X-ray region.
A. Which region of the electromagnetic spectrum has the highest frequency?
B. Which region of the electromagnetic spectrum has the longest wavelength?
C. Which region of the electromagnetic spectrum will travel with the fastest speed?