Mechanical Waves
How is a transverse wave different from a longitudinal wave?
A transverse wave travels perpendicular to the motion of the wave while a longitudinal wave travels parallel to the motion of the wave.
What makes electromagnetic waves different from mechanical waves in terms of how they travel?
Electromagnetic waves are faster than mechanical waves (speed of light) and they can travel through a vacuum.
What is the difference between pitch and volume in sound?
Pitch is dependent on frequency while sound (loudness) is dependent on amplitude.
What is constructive interference and what does it do to the wave's amplitude?
It is when two waves traveling through the same medium meet and result in one "bigger" wave (bigger amplitude). Crests & troughs line up.
Define frequency and explain what units it is measured in.
Frequency is the number of complete waves that pass a certain point each second. Measured in Hertz.
Why do mechanical waves travel faster through solids than gases?
Because the molecules are more tightly packed so the energy from the wave can easily bounce off particles in a solid.
Place all the waves on the EMS in order from lowest to highest frequency.
Radio waves, Microwaves, Infrared Radiation, Visible Light, Ultraviolet, X-rays, Gamma Rays
What causes the Doppler Effect to occur?
Either an observer moving in relation to a sound or a sound moving in relation to an observer.
What happens to a wave when it reflects off a surface? Think about angle.
It bounces off that surface and the angle of incidence = angle of reflection
A wave diagram shows that the distance between crests is decreasing over time. What can you infer about frequency? Justify your answer.
That frequency is increasing. This is because as crests get closer together, the wavelength decreases. Wavelength & frequency have an inverse relationship so frequency would increase.
How can you increase the energy of a mechanical wave without changing its frequency?
Change its amplitude.
Why do people get headaches when looking at screens for too long?
The blue light in the screens is one of the harsher visible light colors so long exposure irritates the eyes.
In the Doppler Effect, what happens to the wavelength of sound in front of a moving source?
The wavelength appears shorter.
Is diffraction easier to observe with longer or shorter wavelengths? Why?
Longer wavelengths because they can bend more easily around obstacles (they are closer in size to the obstacle or opening).
Why do waves often become weaker the farther they travel from their source?
Because their energy spreads out and gets absorbed by the medium. The same energy is distributed over a larger area and the medium causes friction/ resistance.
A student says, "Waves carry matter from one place to another." Use evidence to support or refute this answer.
Waves carry energy from one place to another, they do not carry matter.
What would happen to the wave speed on the EMS if you increased the amplitude of the waves?
Nothing. They all travel at the speed of light and only change speed when traveling through different media.
A student claims that sound travels the same speed in all gases. Support or refute this claim using evidence.
Different gases have different molecular masses & properties. They can also exist at various temperatures, so the student's claim is incorrect, as speed would vary.
How can you tell the difference between refraction and diffraction when observing waves?
Refraction is when a wave bends due to a change in medium. Diffraction is when a wave spreads out passing through an opening or around an object.
Explain why the same sound note can be heard as louder in one room than another even if it comes from the same source.
The room changes how the sound waves behave (reflection, absorption, interference, room shape & size). All these behaviors can affect how loud the sound appears.
Design a test to determine whether a wave is transverse or longitudinal without being told which one it is. Describe what observations you would look for.
Use a spring or slinky that has a bright colored tape on one point of the slinky. Create a pulse and watch which direction the disturbance travels. Generate a wave again and focus only on the marked point (does it move perpendicular or parallel to the direction of the disturbance). If it moves perpendicular it is transverse, if it moves parallel it is longitudinal.
Why do microwaves heat food but not usually heat plastic plates as much?
Because the microwaves interact with the water molecules in the food, causing them to vibrate and heat the food up. Plastic plates do not have enough water molecules in order for them to be heated.
A sound wave enters water from air. The speed increases, but the source frequency stays the same. Explain what must happen to the wavelength & why.
If speed increases but frequency stays the same, the wavelength has to increase (get longer). Because speed = wavelength x frequency.
Why does a green piece of paper appear green?
It reflects the wavelength for green light and absorbs all other wavelengths of the visible spectrum.
A wave has very high frequency but low amplitude. Compare its energy to a wave with low frequency but high amplitude and explain which likely carries more energy in a mechanical system.
In a mechanical wave, amplitude is what affects the amount of energy a wave has. Therefore, the low frequency, high amplitude wave would likely carry more energy.