Topic 3.1 - General Wave Properties

Question 1

What is a wave?

Answer 1

A regular disturbance transferring energy in the direction of the wave’s propagation without transferring matter.

Question 2

What is a transverse wave?

Answer 2

A wave in which oscillations are at right angles (perpendicular) to the direction of motion.

Question 3

Give examples of transverse waves

Answer 3

Waves on a string, all electromagnetic waves (eg. visible light), ripples on water, vibrations on guitar strings

Question 4

What is a longitudinal wave?

Answer 4

A wave where the oscillations are parallel to (in the same direction as) the direction of motion.

Question 5

Give examples of longitudinal waves

Answer 5

Pulses along a spring, sound waves, ultrasound

Question 6

Transverse waveforms have…

Answer 6

Peaks and troughs

Question 7

Longitudinal waveforms have…

Answer 7

Compressions and rarefactions

Question 8

Wavelength is…

Answer 8

The wavleegth of a wave is the distance between succesive crests

Question 9

Frequency is…

Answer 9

The number of complete waves passing a given point per second, or the number of waves per second produced by the source.

Question 10

State the wave equation

Answer 10

v =λ x f

• v = velocity (m/s)
• λ = wavelength (m)
• f = frequency (Hz)

Question 11

What is refraction?

Answer 11

Refraction is the change in speed of a wave when crossing a boundary between two media, resulting in a change in direction.

Question 12

Which property of a wave is not changed by refraction?

Answer 12

The frequency.

Question 13

What happens when waves are incident on a flat surface?

Answer 13

Reflection

Question 14

stronger reflected wave is produced when…

Answer 14

The surface is smoother

Question 15

Why do rough surfaces appear matt when illuminated?

Answer 15

The reflected light rays are scattered in all directions.

Question 16

When entering a denser material, light waves…

Answer 16

…slow down and bend towards the

normal.

Question 17

When entering a less dense material, light waves…

Answer 17

…speed up and bend away from the normal.

Question 18

What is diffraction?

Answer 18

The spreading out of waves passing through a narrow gap or across an edge.

Question 19

What size of gap produces the largest diffraction?

Answer 19

A gap of the same width as the wavelength of the wave passing through it.

Question 20

What is a ripple tank?

Answer 20

A shallow glass tank with an oscillating paddle/needle to create waves. It is illuminated from above so waves can be seen on the surface below the tank

Question 21

Describe how to demonstrate reflection using a ripple tank.

Answer 21

Waves will reflect off the glass sides of the tank.

Question 22

Describe how to demonstrate refraction using a ripple tank.

Answer 22

Place a glass box across half of the floor of the ripple tank. The waves will change speed when travelling through the less dense area.

Question 23

Describe how to demonstrate diffraction using a ripple tank.

Answer 23

Place two glass blocks in the middle of the tank, leaving a small gap, and observe the wave patterns.

Question 24

Transerve wave being sent along a rope

Answer 24

Question 25

What is the amplitude of a wave

Answer 25

The amplitude is defined as the maximum displacement (movement away) from the rest or undisturbed level.

Question 26

What are the three ways a wave’s direction of motion can change?

Answer 26

• Refraction
• Reflection
• Diffraction

Question 27

How many ways can a wave change at a boundary?

Answer 27

3 times (refraction, reflection, diffraction)

Question 28

Diffraction with different gaps

Answer 28

• If the gap size is very large relative to the size of the wavelength, the wave passes through with little diffraction.
• If the gap size is very small relative to the size of the wavelength, the amount of diffraction increases but not much of the wave will pass through the gap.

Question 29

What causes a wave to diffract

Answer 29

• Corners
• Single edges
• Gaps

Question 30

What happens when waves hit plane barriers?

Answer 30

• When a wave hits a smooth plane barrier, it is reflected so that its angle of incidence equals the angle of reflection
• When a wave hits a rough plane barrier, it is mostly refracted; the wave bends and travels through the plane barrier instead of reflecting

Question 31

Interpret reflection and refraction using wave theory.

Answer 31

Angle of incidence = angle of reflection