When waves are reflected, absorbed or passed through
Grade 8 Science Worksheet - Building Confidence
Circle the best answer, or write your answer on the line.
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Light on three materials (example data)
material reflected (%) absorbed (%) Clear glass 8 2 Tinted glass 6 54 Mirror 95 4 Light that is not reflected or absorbed is transmitted.
Ari tests three materials with a flashlight. What percent of the light does the tinted glass transmit?
Bo shines a lamp on three materials. What percent of the light does the window film transmit?
A lamp shines on three materials. What percent of the light does the lampshade transmit, Esme?
Panels tested with the same sound (example data)
panel reflected (%) absorbed (%) transmitted (%) Foam 10 85 5 Plaster 80 5 15 Plywood 55 10 35 Jun wants to cut echoes in a music room. Which panel should cover the walls?
- Plywood, since 35% of the sound passes through it, which is the most of any panel here
- Foam, since it reflects just 10% of the sound and absorbs 85% of it
- Plaster, since it reflects 80% of the sound, and reflecting is how a wall takes sound away
- Plaster, since it is the hardest panel, and hard walls soak up the most sound
Materials tested with a lamp (example data)
material reflected (%) absorbed (%) transmitted (%) Polished metal 95 5 0 White paper 80 20 0 Black paper 5 95 0 Glass 8 2 90 Luz wants to make a mirror. Which material should be the reflecting layer?
- Black paper, since it takes in 95% of the light, and a mirror is a surface that takes light in
- Glass, since 90% of the light passes through it, the largest number in its column
- Polished metal, since it sends back 95% of the light that strikes it
- White paper, since it reflects 80% of the light, and paper is the cheapest of the four
Mirror test (example data)
angle of incidence from the normal (°) angle of reflection from the normal (°) 30 30 45 45 70 70 A ray leaves a mirror at 25° from the normal. What was its angle of incidence from the normal, Noah?
- 65°, the angle between the incoming ray and the mirror surface
- 25° from the normal, equal to the angle of reflection
- 50°, the angle between the incoming ray and the reflected ray
- 20°, since the light lost some energy on the way into the mirror
A ray strikes a mirror at 30° to the mirror's surface. What is its angle of reflection from the normal, Pia?
- 60° from the normal, since the ray is 90° − 30° from it
- 30°, the angle the question gives, which is already the angle of reflection
- 90°, since the ray turns a right angle at a flat mirror
- 120°, the angle between the incoming ray and the reflected ray
Cloth in sunlight for 10 minutes (example data)
cloth temperature rise (°C) Black 14 White 5 A black cloth warmed more than a white cloth in the sun. Which explanation fits the data, Ren?
- The black cloth absorbed more light, and absorbed light energy becomes thermal energy
- The white cloth absorbed the light, and the absorbed energy vanished, so it stayed cool
- The black cloth reflected the most light, and reflected light is what heats a cloth
- The black cloth transmitted more light, which warmed the air trapped under it
Foam on a studio wall absorbs sound. What happens to the sound energy it absorbs, Tala?
- It is stored in the foam as sound and released the next day as an echo
- It disappears, since energy is used up when a wave is absorbed
- It becomes a very small amount of thermal energy in the foam
- It bounces back out of the foam as a quieter echo, and that counts as absorbing it
Echo length in a gym (example data)
room echo lasts (s) Bare gym 2 Gym with mats on the walls 0.6 Mats on the walls shortened a gym's echo. Which explanation fits the data, Zee?
- The mats made the gym smaller, and a smaller room has a shorter echo whatever is on its walls
- The mats reflected the sound up toward the ceiling, and reflecting quiets a room as absorbing does
- The mats absorbed some of the sound, so less was reflected back and the echo faded sooner
- The mats made the air in the gym colder, so the sound traveled slower and faded away