Waves

Question 1

What are waves?

Answer 1

Waves are oscillations or vibrations of particles. They transfer energy, not matter. (e.g in a sound wave, the air particles vibrate back and forth, causing compressions and rarefactions. None of the particles in my lungs reach your ears)

Question 2

What is frequency?

Answer 2

Measured in Hz - the number of waves passing a point each second

Question 3

What is amplitude?

Answer 3

Measured in m - Maximum height of the wave measured from the middle.

Question 4

What is wavelength?

Answer 4

Measured in m - The shortest distance between two coherent points on the same wave, e.g the distance from peak to peak

Question 5

What are longitudinal waves?

Answer 5

Oscillations parallel to wave motion

Question 6

What are examples of longitudinal waves?

Answer 6

Sound, P-waves (earthquakes), mechanical waves

Question 7

What are transverse waves?

Answer 7

Oscillations perpendicular to wave motion

Question 8

What are examples of transverse waves?

Answer 8

Light (all electromagnetic radiation), S-waves (earthquakes), water waves, waves on strings

Question 9

What is the calculation for wave speed?

Answer 9

Wave speed = Frequency x Wavelength

m/s = Hz x m

Question 10

What is refraction?

Answer 10

Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction and this effect is called refraction.

Refraction doesn’t happen if the waves cross the boundary at an angle of 90° (called the normal) - in that case they carry straight on.

Question 11

What is diffraction?

Answer 11

When waves meet a gap in a barrier, they carry on through the gap. However, the waves spread out to some extent into the area beyond the gap. This is called diffraction.

The extent of the spreading depends on how the width of the gap compares to the wavelength of the waves. Significant diffraction only happens when the wavelength is of the same order of magnitude as the gap.

Question 12

What is reflection?

Answer 12

Sound waves and light waves reflect from surfaces. When waves reflect, they obey the law of reflection:
“The angle of incidence equals the angle of reflection”

The normal is a line drawn at right angles to the reflector
The angle of incidence is between the incident (incoming) ray and the normal
The angle of reflection is between the reflected ray and the normal.

Question 13

What do amplitude and frequency affect in a sound wave?

Answer 13

The greater the amplitude, the louder the sound.

The greater the frequency, the higher the pitch.

Question 14

What is the electromagnetic spectrum?

Answer 14

Radio waves
Microwaves
Infrared
Visible
Ultra Violet
X-rays
Gamma Rays

Question 15

What increases in the electromagnetic spectrum?

Answer 15

The energy, frequency, and wavelength

Question 16

Describe the Doppler Effect. (6)

Answer 16

If someone is standing still, and if something is approaching them at a constant speed, the sound waves in front are squashed and become closer together, which increases the frequency and means the person in front hears a higher pitched sound. The same happens if you are standing behind the vehicle, the waves become further apart which gives a lower frequency and means the sound has a lower pitch.