Waves: Light and Sound — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
In Grade 4 we learn the eardrum vibrate when sound waves hit it.
Corrected: In Grade 4 we learn the eardrum vibrates when sound waves hit it.
Subject-verb agreement: singular 'eardrum' takes 'vibrates'.
2. Fix the sentence:
Grade 4 students knows that eyes detect light waves and send signals to the brain.
Corrected: Grade 4 students know that eyes detect light waves and send signals to the brain.
Plural subjects use the base form: 'students know', not 'students knows'.
3. Fix the sentence:
The brain interpret the signals from the ears and eyes in Grade 4 lessons.
Corrected: The brain interprets the signals from the ears and eyes in Grade 4 lessons.
Singular subject 'brain' requires 'interprets' for agreement.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. In Grade 4, the thin skin inside your ear that vibrates with sound is called the eardrum.
The eardrum vibrates when sound waves enter the ear canal.
2. Grade 4 science: our eyes detect light waves that bounce off objects around us.
Eyes are sensors that detect light waves and send signals to the brain.
3. The brain receives signals from the ears and eyes and tells us what we hear and see in Grade 4.
The brain interprets nerve signals into sounds and images.
4. A nerve message traveling from the ear to the brain is called a signal in Grade 4 lessons.
Sense organs change waves into signals the brain can read.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. In Grade 4 words, explain what happens inside your ear when a friend claps nearby.
Sample answer: Sound waves from the clap travel through the air and push on my eardrum. The eardrum vibrates and sends signals through nerves to my brain, which understands the sound as a clap.
Hearing is a chain: wave hits eardrum, vibration becomes a signal, brain interprets.
2. Grade 4 question: how do your eyes and brain work together to let you see a red apple?
Sample answer: Light waves bounce off the red apple and enter my eyes. My eyes turn the light into signals that travel along nerves to my brain. The brain reads the signals and tells me I see a red apple.
Vision uses reflected light, sensor cells in the eye, and brain interpretation.