Physics: Waves: Sound and Light Properties
Comparing how sound and light waves travel, reflect, refract, and carry energy
Physics: Waves: Sound and Light Properties
Comparing how sound and light waves travel, reflect, refract, and carry energy
Physics - Grade 6-8
- 1
A student taps a metal desk and hears a sound. Explain how the sound travels from the desk to the student's ear.
Think about particles vibrating back and forth.
The tap makes the desk vibrate. The vibrations transfer energy to nearby air particles, creating a sound wave that travels through the air to the student's ear. - 2
Light from the Sun can reach Earth through space, but sound from the Sun cannot. Explain why.
Light is an electromagnetic wave, so it can travel through empty space. Sound is a mechanical wave, so it needs matter such as air, water, or solid material to travel. - 3
Two sound waves are shown. Wave A has a larger amplitude than Wave B, but both have the same frequency. Which sound is louder, and why?
Amplitude is related to loudness for sound.
Wave A is louder because a larger amplitude means the sound wave carries more energy and is heard as a louder sound. - 4
A flute plays a note with a high pitch. A tuba plays a note with a low pitch. Compare the frequencies of the two sounds.
The flute sound has a higher frequency than the tuba sound. Higher frequency sound waves are heard as higher-pitched sounds. - 5
A wave has a frequency of 5 hertz and a wavelength of 2 meters. Use the formula speed = frequency × wavelength to find the wave speed.
Multiply the frequency by the wavelength.
The wave speed is 10 meters per second because 5 hertz × 2 meters = 10 meters per second. - 6
A sound wave travels through air at about 340 meters per second. If the sound has a frequency of 170 hertz, what is its wavelength? Use wavelength = speed ÷ frequency.
The wavelength is 2 meters because 340 meters per second ÷ 170 hertz = 2 meters. - 7
A student shines a flashlight at a mirror. The beam bounces off the mirror. Identify the wave behavior and describe what happens.
A mirror is a surface that bounces light back.
The wave behavior is reflection. The light wave bounces off the mirror surface and changes direction. - 8
A pencil looks bent when it is placed in a glass of water. Identify the wave behavior that causes this effect and explain it.
This happens when light passes between two different materials.
The wave behavior is refraction. Light changes speed and direction when it passes from air into water, making the pencil appear bent. - 9
A black shirt feels warmer than a white shirt in bright sunlight. Use wave properties to explain why.
The black shirt absorbs more light energy and changes it into thermal energy. The white shirt reflects more light, so it absorbs less energy and feels cooler. - 10
Classify each material as mostly transparent, translucent, or opaque: clear window glass, wax paper, and a wooden door.
Transparent means clear, translucent means partly clear, and opaque means blocking light.
Clear window glass is mostly transparent because light passes through clearly. Wax paper is translucent because it lets some light through but scatters it. A wooden door is opaque because it blocks light. - 11
A teacher claps once in a gym and hears the sound repeat a moment later. What is this repeated sound called, and what causes it?
The repeated sound is an echo. It is caused by sound waves reflecting off a surface, such as a wall, and traveling back to the listener. - 12
Visible light is part of the electromagnetic spectrum. Arrange these colors from shortest wavelength to longest wavelength: red, violet, green.
In visible light, violet has shorter wavelengths and red has longer wavelengths.
The order from shortest wavelength to longest wavelength is violet, green, red. Violet light has a shorter wavelength than green light, and red light has the longest wavelength of the three. - 13
A siren seems higher-pitched as an ambulance moves toward you and lower-pitched as it moves away. Name this effect and explain what changes.
This is the Doppler effect. As the ambulance moves toward you, the sound waves are compressed and the frequency is higher. As it moves away, the waves are stretched out and the frequency is lower. - 14
A student says, 'A louder sound must be traveling faster than a quieter sound in the same room.' Explain whether the student is correct.
Loudness is connected to amplitude, not wave speed.
The student is not correct. In the same material and conditions, sound waves travel at about the same speed. A louder sound has a greater amplitude, not a greater speed. - 15
Compare sound waves and light waves by listing one way they are similar and one way they are different.
Sound waves and light waves are similar because both can carry energy and can reflect. They are different because sound needs a material medium to travel, while light can travel through empty space.