Waves: Light and Sound — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. The distance from one wave peak to the next peak is called the wavelength.
Grade 4 students learn that wavelength is a horizontal measurement of a wave. Long wavelengths and short wavelengths look different on a wave diagram.
2. The height of a wave from the middle line up to the top is called the amplitude.
In Grade 4 science, amplitude controls energy. Larger amplitude in sound waves means louder; larger amplitude in light waves means brighter.
3. The number of waves that pass a point in one second is the wave's frequency.
Grade 4 learners connect frequency to pitch in sound and to color in light. Higher frequency sound is higher pitch; higher frequency light looks more violet/blue.
4. A drum hit very softly makes a sound wave with a small amplitude, so the sound is quiet.
In Grade 4 science, the energy you put into a vibration changes the amplitude. Less energy means a smaller wave and a quieter sound.
5. A flute note that is very high in pitch has a higher frequency than a low tuba note.
Grade 4 students compare frequencies between instruments. The flute vibrates faster, so it has more waves per second and a higher pitch.
6. Two sound waves with the same wavelength but different amplitudes will sound the same in pitch but different in volume.
In Grade 4 science, separating pitch (frequency/wavelength) from volume (amplitude) is a key skill. Same wavelength keeps the pitch; different amplitude changes loudness.
7. On a wave diagram, the lowest point of the wave is called a trough.
Grade 4 wave vocabulary includes crest (top), trough (bottom), wavelength (crest-to-crest), and amplitude (middle line to crest).
8. Light waves that have a short wavelength and high frequency look more blue to our eyes.
In Grade 4 science, blue and violet light have shorter wavelengths and higher frequencies than red light, which has longer wavelengths.
9. When a vibration sends out energy that travels through air or water, that moving energy is called a wave.
Grade 4 students learn that a wave is a pattern of moving energy. Both sound and light travel as waves with measurable properties.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Wavelength
→ Distance from one peak to the next peak
Distance from one peak to the next peak
Amplitude
→ Height of the wave from middle to top
Height of the wave from middle to top
Frequency
→ Number of waves per second
Number of waves per second
Crest
→ The very top point of a wave
The very top point of a wave
Grade 4 learners use these four wave terms to describe both sound and light. Knowing each definition helps them read wave diagrams in NGSS 4-PS4.