Waves: Light and Sound — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. In Grade 4 science, what kind of waves do radios use to send music to listeners?
A) Water waves
B) Sound waves only
C) Radio waves
D) Earthquake waves
Radio stations broadcast information using radio waves through the air.
2. Grade 4: Morse code uses short and long ___ to spell out letters.
A) Sounds or flashes
B) Colors
C) Smells
D) Tastes
Morse code turns letters into patterns of beeps or light flashes.
3. Grade 4 question: optical fibers are thin glass strands that carry information using what?
A) Pulses of light
B) Strong magnets
C) Hot steam
D) Loud noise
Optical fibers send data as light pulses through clear glass.
4. In Grade 4 lessons, a telephone changes your voice into a ___ that travels along wires.
A) Signal
B) Color
C) Solid
D) Shadow
Phones turn sound waves into electrical signals for transmission.
Part B: Fill in the Blank
Write the correct answer on each line.
1. In Grade 4 science, the system of dots and dashes used to send messages is called Morse code.
Morse code uses short and long signals to represent letters.
2. Grade 4: thin glass strings that carry pulses of light are called optical fibers.
Optical fibers transmit data as light over long distances.
3. Sending a message from a sender to a receiver is called communication in Grade 4 lessons.
Communication is the exchange of information using signals.
4. An electrical message that carries information through wires is called a signal in Grade 4 science.
Devices encode information as signals for fast transmission.
5. The act of sending a wave or signal between two places is called transmission in Grade 4 lessons.
Transmission moves signals from a source to a receiver.