# Waves, Sound & Light in Physics Flashcards

Waves, Sound & Light in Physics Flashcards
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Constructive Interference

Occurs when two waves that meet and the trough of one wave lines up with the trough of another, making the amplitude of the resulting wave larger

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Diffraction

The process by which light wave bends around an obstacle and spreads out

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A light ray passes from water (n = 1.33) into glass (n = 1.50) at an angle of incidence of 40 degrees. Find the angle of refraction.

n1 * sin(θ1) = n2 * sin(θ2)

1.33 * sin(40°) = 1.50 * sin(θ2)

θ2 = 34.7°

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Index of Refraction

A value that describes how the speed of light in a medium differs from the speed of light in a vacuum

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Law of Reflection

Angle of incidence = angle of reflection

θ i = θ r

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Longitudinal Wave

A type of wave in which the vibrations are parallel to the wave's direction

Requires a medium to travel through

Example: sound waves

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Transverse Wave

A type of wave in which the vibrations are perpendicular to the wave's direction

Examples: electromagnetic waves, seismic waves

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Wave Speed

The distance a wave travels in a given amount of time

v = λf

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Wave Frequency

The number of waves that pass a fixed area per second

Measured in Hertz

Equal to the inverse of the wave period (1/T)

Symbol: f

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Wavelength

The distance between identical parts on two consecutive wave, such as from the crest of one wave to the next

Symbol: λ

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Wave Amplitude

The height of a wave's crest or trough from its resting position

Measures the amount of energy a wave has

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Wave

A disturbance that travels and transfers energy between two places

Actions whose nature can be described like a wave: spring on a weight, pendulums, water waves, stadium 'waves'

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Electromagnetic Wave

A type of wave that does not require a medium to travel through

Examples: radio waves, visible light, gamma rays

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Mechanical Wave

A type of wave that requires a medium to travel through

Examples: sound waves, seismic waves

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## Flashcard Content Overview

You have no doubt seen a picture or a video of a surfer catching a wave. But did you know that ocean waves are just one type of wave? There are many waves you interact with every day. When you talk, you are making sound waves. If you go to the doctor and get an X-ray, waves help your doctor capture the image of your bones. Your cell phone uses waves, as does your television. These flashcards will introduce you to the characteristics of different types of waves.

Front
Back
Mechanical Wave

A type of wave that requires a medium to travel through

Examples: sound waves, seismic waves

Electromagnetic Wave

A type of wave that does not require a medium to travel through

Examples: radio waves, visible light, gamma rays

Wave

A disturbance that travels and transfers energy between two places

Actions whose nature can be described like a wave: spring on a weight, pendulums, water waves, stadium 'waves'

Wave Amplitude

The height of a wave's crest or trough from its resting position

Measures the amount of energy a wave has

Wavelength

The distance between identical parts on two consecutive wave, such as from the crest of one wave to the next

Symbol: λ

Wave Frequency

The number of waves that pass a fixed area per second

Measured in Hertz

Equal to the inverse of the wave period (1/T)

Symbol: f

Wave Speed

The distance a wave travels in a given amount of time

v = λf

Transverse Wave

A type of wave in which the vibrations are perpendicular to the wave's direction

Examples: electromagnetic waves, seismic waves

Longitudinal Wave

A type of wave in which the vibrations are parallel to the wave's direction

Requires a medium to travel through

Example: sound waves

Law of Reflection

Angle of incidence = angle of reflection

θ i = θ r

Index of Refraction

A value that describes how the speed of light in a medium differs from the speed of light in a vacuum

A light ray passes from water (n = 1.33) into glass (n = 1.50) at an angle of incidence of 40 degrees. Find the angle of refraction.

n1 * sin(θ1) = n2 * sin(θ2)

1.33 * sin(40°) = 1.50 * sin(θ2)

θ2 = 34.7°

Diffraction

The process by which light wave bends around an obstacle and spreads out

Constructive Interference

Occurs when two waves that meet and the trough of one wave lines up with the trough of another, making the amplitude of the resulting wave larger

Destructive Interference

Occurs when two waves that meet and the trough of one wave lines up with the crest of another, making the amplitude of the resulting wave smaller

Find the frequency of a sound wave travelling at 330 m/s with a wavelength of 10 m.

v = λf

330 m/s = 10 m * f

f = 33 Hz

The speed of sound at room temperature is 346 m/s. Determine how the wavelength of a 50 Hz wave changes when the temperature drops, which decreases the speed of sound.

λ = 346 m/s / 50 Hz = 6.92 m

At colder temp, speed decreases

λ = 340 m/s / 50 Hz = 6.8 m

As wavelength decreases, the speed of sound decreases.

Intensity and Sound

Measured in decibels on a logarithmic scale

Higher intensity = louder sound

Pitch and Sound

How frequency is perceived

High pitched sound = high frequency

Low pitched sound = low frequency

Human ears have limited pitch ranges that can be perceived

A parked car is turned on, its engine making a sound that is 450 Hz. As it approaches, the engine makes a sound that is 480 Hz. Find the speed of the car if the speed of sound is 350 m/s.

f' = (v + v0) / (v + vs) * f

480 Hz = (350 m/s + 0) / (350 m/s - vs) * 450 Hz

vs = 21.9 m/s

Doppler Effect and Sound

A change in the perceived pitch of sound waves due to an object moving closer (higher pitch) to or away from (lower pitch) the observer

Relationship between Wavelength and Diffraction

Larger wavelengths = smaller frequencies = more diffraction

Smaller wavelengths = larger frequencies = less diffraction

Electromagnetic Spectrum

In order of increasing frequency/decreasing wavelength: radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays

White Light

The color of light that includes all the visible light frequencies

Wave-Particle Duality of Light

A theory that states that wave behaves as both a wave and a particle

Photoelectric Effect

A phenomenon that occurs when matter absorbed light energy, causing electrons to become excited and emitted

Find the energy carried by a photon of blue light with a wavelength of 460 nm. (Plank's constant = 4.136 * 10-15 eV/Hz)

v = λf

3.0 * 108 m/s = 4.6 * 10-7 m * f

f = 6.5 * 1014 Hz

E = hf = (4.136 * 10-15 eV/Hz) * (6.5 * 1014 Hz) = 2.7 eV

Spherical Mirrors

Types: concave (on inside of spherical surface) or convex (on outside of spherical surface)

Can produce images that are distorted: upside-down, different sized

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