Flashcards: Characterizing Wave Phenomena — 35 cards

What is sound intensity in physics?

Energy transported by a sound wave per unit time and area.

What is the audibility threshold intensity value?

$1.0 \times 10^{-12}\ \mathrm{W\,m^{-2}}$

What is the pain threshold intensity for sound?

$1\ \mathrm{W\,m^{-2}}$

What is the formula for sound intensity level in decibels?

$L = 10\log\left(\frac{I}{I_0}\right)$

How is geometric attenuation of sound caused?

By spreading the same power over larger spheres as distance increases.

What causes absorption attenuation of sound?

A material between source and receiver reduces sound intensity.

What is diffraction in wave behavior?

Diffraction is the spreading of a wave after passing through an opening smaller or equal to its wavelength.

Which types of waves exhibit diffraction?

Both mechanical waves and light waves exhibit diffraction.

What does diffraction demonstrate about light?

Diffraction demonstrates the wave nature of light.

When is diffraction more pronounced regarding opening size?

Diffraction is more pronounced when the opening size is close to or smaller than the wavelength.

What formula gives the diffraction angle $\theta$ in radians?

The diffraction angle satisfies $\theta = \frac{\lambda}{a}$.

In $\theta = \frac{\lambda}{a}$, what does $a$ represent?

$a$ represents the opening size.

What is the formula for opening size $a$ using central spot width $L$ and distance $D$?

The opening size is $a = \frac{2\lambda D}{L}$.

What approximation is used in $a = \frac{2\lambda D}{L}$?

The small-angle approximation is used.

What is interference in wave physics?

The superposition of two waves producing reinforcement and cancellation.

What conditions are required for observable interference?

Waves must have the same wavelength or frequency and be synchronous.

When does constructive interference occur between waves?

When waves are in phase and their amplitudes add.

When does destructive interference occur between waves?

When waves are in opposite phase and their amplitudes cancel.

What is the path difference formula for constructive interference?

$\delta = k\lambda$ with k an integer.

What is the path difference formula for destructive interference?

$\delta = \left(k+\frac{1}{2}\right)\lambda$ with k an integer.

How do noise-cancelling headphones reduce ambient noise?

They generate an opposite-phase signal to cancel ambient sound.

What acts as two synchronous sources in Young's double-slit experiment?

The two slits separated by distance e.

What is the formula for optical path difference at point M on the screen?

$\delta = \frac{e x}{D}$

What does the interfringe represent in Young's double-slit experiment?

The smallest distance between two consecutive constructive interference points.

What is the formula for the Young double-slit interfringe?

$i = \frac{\lambda D}{e}$

What is the Doppler effect?

A change in wave frequency perceived when source moves relative to observer.

How does frequency change when the source approaches the observer?

The perceived frequency increases and the sound is higher.

How does frequency change when the source recedes from the observer?

The perceived frequency decreases and the sound is lower.

What is the formula for received frequency when the source approaches at speed v?

$f_R = f_e\frac{c}{c-v}$

What is the formula for received frequency when the source recedes at speed v?

$f_R = f_e\frac{c}{c+v}$

What is the Doppler frequency shift formula?

$\Delta f = f_R - f_e = f_e\frac{v}{c-v}$

What is the approximate Doppler frequency shift when v is much smaller than c?

$\Delta f \approx f_e\frac{v}{c}$

How are wavelength and frequency related in a wave?

They vary inversely according to $\lambda = \frac{c}{f}$.

What is redshift in astronomy?

It is the shift of stellar spectral lines toward longer wavelengths when a star moves away.

How do astronomers identify stellar motion?

By comparing a star's emitted spectrum with the laboratory spectrum of the element.