Focal Length
The Distance From A Lens To Its Focal Point, Determining Image Formation.

Lens
A Transparent Object That Refracts Light To Form Images, Described In Optics.

Optics
A Branch Of Physics That Studies The Behavior Of Light, Including Reflection And Refraction.

Decibel
A Logarithmic Unit Used To Measure The Intensity Of Sound Waves.

Intensity
The Power Per Unit Area Carried By A Wave, Related To Amplitude.

Sound Wave
A Longitudinal Wave That Travels Through A Medium Such As Air Or Water.

Doppler Effect
A Change In Observed Frequency Due To Relative Motion Between A Source And An Observer.

Resonance
A Phenomenon In Which A System Oscillates With Maximum Amplitude When Driven At Its Natural Frequency.

Standing Wave
A Wave Pattern Formed By The Interference Of Two Waves Traveling In Opposite Directions.

Wave Speed
The Speed At Which A Wave Travels, Equal To Wavelength Times Frequency.