Physics Test on Wave, Sound, and Light

frequency (f) is the…

# of cycles/time

the unit for frequency

Hertz (Hz)

period (T) is…

1/f

Characteristics of a Wave

• a wave is a ripple in TIME and SPACE

• All waves are created by a vibrating space

• Waves transport energy

crest

the highest peak of a wave

amplitude

the distance (length) of a wave from equilibrium

lambda (λ)

wavelength, how wide each wave is from a cycle

trough

the lowest point of a wave

wave equation

v = f × λ

frequency ≡ pitch

amplitude ≡ volume

ultrasound

above sound

infrasonic

below sound

echo (round trip)

∆s= v∆t/2

formula for intensity

I (intensity of sound) = Power/ Area

• Area of a sphere: 4πr²

What is β?

β = 10log(I/I₀)

• I₀: 10⁻¹² ω/m² or IE-12 ω/m²

At the thereshold of hearing, β = ?

0 dB

Harmonic formula of a closed tubes

fₙ = nv/4l

• n = 1,3,5,7,9…

Harmonic formula of an open tube

fₙ= nv/2l

• n = 1,2,3

Mechanical Waves

need a medium to travel through (ex: sound or slinky)

Transverse waves

• vibrate perpendicular to the motion vibration (ex: light and water waves)

Longitudinal waves

sound waves

Electromagnetic Waves

• do NOT need a medium but it CAN travel through one

• can travel through a vacuum (space) where they are FASTER

• also produced by a vibrating source of electrons

• ex: microwaves, ultraviolet t(sun) rays, gamma rays, x-rays, infrared rays, and radio

Resonance

• are forced vibrations

• ex: instruments

• change the amplitude

Doppler Effect

• the apparent (not actually) change in frequency due to relative motion

• sound (car honking or fire truck siren)

  • the frequency ≡ pitch (it is higher and screechier as it comes towards you, then lower as it goes away from you)

• light ≡ Red shift

  • frequency ≡ color

Reflection

to bounce back

Tight-end

out of phase

Loose end

inphase

Refraction

to bend due to change of speed

• only get refraction when you change mediums

Defraction

to spread out because the wave is bigger than the opening

Interference (to combine or add and subtract) can be…

constructive or destructive

c (speed of light) is…

3.00E8 m/s

deci

10⁻¹

centi

10⁻²

milli

10⁻³

micro (mc)

10⁻⁶

nano (n)

10⁻⁹

pico (p)

10⁻¹²

deca (d)

10¹

hecto (h)

10²

kilo (k)

10³

Mega (M)

10⁶

Giga (G)

10⁹

Tera (T)

10¹²

Plank’s constant

h = 6.63 × 10⁻³⁴ Js

# of beats =

|f₁-f₂|

AM

amplitude modulated

• measured in kilohertz

• ex: KYW 1060 station has a frequency of 1060 kHz

FM

frequency modulated

• measured in Megahertz

• ex: 98.1 radio station has a frequency of 98.1 × 10⁶ MHz

Defraction

530 groove per millimeters

Light

is a wave proved by Christaan Huygens