Waves: Light and Sound — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A Grade 4 student yells in an empty gym and hears their voice come back. What is this called?
A) Refraction of sound
B) Echo (reflection of sound)
C) Absorption of sound
D) Vibration of sound
In Grade 4 science, an echo is sound that has reflected off a hard surface and traveled back. Empty gyms have hard walls and few soft items to absorb the sound.
2. Which room would have the fewest echoes for a Grade 4 reading club?
A) A tiled bathroom with hard walls.
B) A carpeted library with cushioned chairs and curtains.
C) An empty gym with wood floors.
D) A concrete parking garage.
Grade 4 learners connect soft, fluffy materials (carpet, cushions, curtains) to sound absorption. Less reflection means fewer echoes and a quieter room.
3. A magnifying glass focuses sunlight into a small bright spot on paper. Which interaction is mainly happening?
A) Sound absorption
B) Light reflection only
C) Light refraction by the lens
D) Vibration of the paper
In Grade 4 science, a magnifying glass is a curved lens that refracts (bends) light rays so they meet at a focus point, concentrating the sun's energy.
4. A flashlight shines on a thick wooden door. What happens to the light?
A) It passes through clearly because wood is transparent.
B) It is mostly blocked because the door is opaque.
C) It is refracted into a rainbow on the other side.
D) It turns into sound waves on the door.
Grade 4 students sort materials as transparent, translucent, or opaque. Wood is opaque, so it blocks light through reflection and absorption, casting a shadow behind it.
Part B: Fill in the Blank
Write the correct answer on each line.
1. A bat finds bugs in the dark by sending out sound and listening for the echoes that bounce back.
In Grade 4 science, echolocation is a real-world use of sound reflection. Bats and dolphins use returning sound waves to map their surroundings.
2. Recording studios put foam on the walls to absorb sound and stop echoes from messing up the music.
Grade 4 learners connect engineering choices to wave behavior. Soft foam absorbs sound waves so the microphones only pick up the singer, not the echoes.
3. A camera lens is curved so it can refract light onto the sensor and make a clear picture.
In Grade 4 science, lenses in cameras, glasses, and telescopes use refraction to focus light. The curve bends rays to form a sharp image.
4. When sunlight hits snow, most of the light is reflected back, which is why snow looks so bright.
Grade 4 students learn that white and shiny surfaces reflect most light. That is also why people wear sunglasses on snowy days.
5. Frosted glass is translucent because it lets some light through but scatters the image so it is blurry.
In Grade 4 science, translucent materials transmit some light but scatter it. The result is brightness on the other side, but no clear picture.