Waves and Energy, Refraction/Reflection/Transmission, Ear, Ultrasound, and Infrasound (Pages 2-4)

A comprehensive set of practice flashcards covering waves, refraction/reflection/transmission/absorption, the ear, ultrasound, and infrasound concepts from Pages 2–4 of the notes.

What do waves transfer and what do they not transfer?

Waves transfer energy but not matter.

Define wavelength.

The distance between the same point on two consecutive waves (e.g., crest to crest).

Define amplitude.

The distance from the equilibrium line to the maximum displacement (crest or trough).

What is frequency?

The number of waves that pass a single point per second.

What is period?

The time taken for a whole wave to completely pass a single point.

What is a wavefront?

The plane in which the wave travels; the direction of the wave.

State the wave speed equation.

v = fλ (velocity equals frequency times wavelength).

What are the units of wave speed?

Metres per second (m/s).

What characterizes transverse waves?

They have peaks and troughs; vibrations are at right angles to the direction of travel.

What characterizes longitudinal waves?

They have compressions and rarefactions; vibrations are in the same direction as travel.

How can you measure the speed of sound in air using a wall?

Make a noise ~50 m from a wall, measure the echo time, then speed = distance/time.

How can you measure wave speed with two microphones and a datalogger?

Record the time difference for sound to travel between microphones; speed = distance/time.

How is wave speed on water measured with a stroboscope?

Use a stroboscope at the same frequency as the water waves and measure the distance between fixed ripples; v = fλ.

How can you estimate wave speed by drawing with a pencil?

Move the pencil at the same speed as the wavefront, measure the time and the line length, then v = distance/time.

What happens to speed, wavelength, and direction when waves refract into a denser medium?

Speed decreases, wavelength decreases, and the wave bends toward the normal.

What is the fundamental rule about refraction direction at a boundary?

The wave changes direction toward the normal when entering a denser medium.

What happens to energy when refraction occurs if frequency remains constant?

Energy remains constant; with decreased speed, wavelength also decreases (since v = fλ and f is constant).

What is reflection in physics?

+Waves reflect off a surface (angle of incidence equals angle of reflection); clearer on smooth surfaces.

How does surface roughness affect reflection?

Smooth surfaces produce stronger reflection; rough surfaces scatter light, making them appear matte.

What is transmission in wave terms?

Waves pass through a transparent material and may refract; more transparent materials transmit more light.

When is light absorbed by a material?

When the light frequency matches the material’s electron energy levels; light is absorbed and converted to heat.

What does it mean if a material appears green?

It reflects green light and absorbs other wavelengths not reflected.

How can substances affect light differently (absorb, transmit, refract, reflect)?

Different wavelengths are absorbed, transmitted, refracted, or reflected depending on the material.

Give an example of a material that transmits and refracts visible light and one that reflects UV light.

Glass transmits and refracts visible light; UV is reflected by glass.

What is the path of sound through the outer ear to the eardrum?

Outer ear collects sound and channels it down the ear canal to the eardrum.

What happens to the eardrum when it is struck by sound waves?

It vibrates at the same frequency as the incoming sound wave.

What role do the tiny bones (ossicles) play in hearing?

They vibrate in response to the eardrum and amplify the sound, transmitting it to the inner ear.

What happens in the cochlea when it receives vibrations?

Fluid movement moves hair cells, which release nerve impulses to the brain; each hair is tuned to a frequency.

Why is the ear only able to hear a limited range of frequencies?

Higher frequency waves carry more energy and can damage cells; the ear has evolved to hear a limited range.

What frequency defines ultrasound?

Frequencies above 20,000 Hz.

What are two uses of ultrasound?

Sonar (depth measurement, detecting shoals) and foetal scanning (imaging the foetus).

What is infrasound and what is its typical frequency range?

Infrasound is sound with frequency below 20 Hz; often used in seismic studies.

What are P-waves and S-waves?

P-waves are longitudinal (compressions) and can pass through solids and liquids; S-waves are transverse and pass only through solids.

What does the detection of only P-waves on the opposite side of Earth suggest about the core?

The Earth's core is liquid; S-waves cannot penetrate it.