Waves: Light and Sound — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A whisper is quieter than a shout because the whisper's sound wave has a smaller amplitude.
Grade 4 students apply amplitude to everyday sounds. Less energy in the voice means a smaller wave and a softer sound.
2. A tiny mouse squeak has a higher pitch than a big lion roar.
In Grade 4 science, faster vibrations make higher pitches. A mouse's tiny vocal cords vibrate faster than a lion's, so the squeak is higher.
3. A bright flashlight sends out light waves with a larger amplitude than a dim flashlight.
Grade 4 learners extend the amplitude idea from sound to light. Bigger amplitude in a light wave means more energy, which our eyes see as brighter.
4. Red light has a longer wavelength than blue light, so red has a lower frequency.
In Grade 4 science, wavelength and frequency are inversely related. Longer wavelength means fewer waves per second, which is a lower frequency.
5. When you shake a jump rope slowly, you make longer wavelengths than when you shake it fast.
Grade 4 students model waves with ropes and slinkies. Slow shakes give long, lazy waves; fast shakes give short, tight waves.
6. A sound wave with the same amplitude but a shorter wavelength will sound higher in pitch.
In Grade 4 science, comparing two sound waves helps students see that wavelength and frequency together control pitch, while amplitude controls volume.
7. Drumming your fingers gently on the desk makes a sound with a small amplitude and a soft volume.
Grade 4 learners feel the link between energy and amplitude. Light taps move air just a little, so the wave is small and the sound is quiet.
8. Light waves and sound waves both have wavelength, amplitude, and frequency.
In Grade 4 science, all waves share three measurable properties. Recognizing this lets students compare sound and light using the same vocabulary.
9. A tuning fork that is hit harder vibrates with a bigger amplitude and makes a louder sound.
Grade 4 students learn that the energy you give a vibrating object equals the loudness of the sound. Hit hard = loud, hit soft = quiet.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Big amplitude in a sound wave
→ Loud sound
Loud sound
Big amplitude in a light wave
→ Bright light
Bright light
Short wavelength of light
→ Bluer color
Bluer color
Short wavelength of sound
→ Higher pitch
Higher pitch
Grade 4 students use this matching to remember that amplitude controls intensity (loud/bright) while wavelength and frequency control pitch and color.