Yr 12 - Waves (1 of 2)

Question 1

What are mechanical waves? & what are they transferred through?

Answer 1

Waves that rely on particles to transfer energy.

• Energy is transferred through a medium.

Question 2

What are EM Waves? & how are they transferred?

Answer 2

Waves that don’t rely on particles to transfer energy.

• Transfer energy through vibrations of electrical and magnetic fields.

Question 3

What is a medium

Answer 3

The substance a wave is travelling through (air for example).

Question 4

What do & don’t waves transfer?

Answer 4

Transfer energy without transferring matter.

Question 5

What’s a progressive wave?

Answer 5

Transfer of energy due to oscillation of medium.

Question 6

Examples of:

• Longitudinal waves
• Transverse waves

Answer 6

Longitudinal - Sound, P-waves

Transverse - Light, S-waves, all EM waves

Question 7

Where is the equilibrium position?

Answer 7

Middle of wave (Horizontally) which the wave travels through.

Question 8

What is meant by Frequency?

Answer 8

Number of waves passing a point per second.

Question 9

What is meant by phase difference?

• Give examples on a graph for a wave.

Answer 9

Difference in phase angle of two waves.

• 0 phase difference between sections 2𝝅 apart (In Phase)
• Sections 𝝅 apart are out of phase by 𝝅
• Sections 1/2𝝅 apart are out of phase by 1/2𝝅

Question 10

What is meant by ‘subtended through 2𝝅’?

Answer 10

The wave has travelled through 2𝝅

Question 11

What Is the phase of a wave?

Answer 11

How far through a wave cycle a certain point has progressed.

• Eg, a wave that has travelled by 1/2𝝅 has phase of 1/2𝝅

Question 12

What is wave speed?

Answer 12

Distance travelled by wave per unit time.

Question 13

What is meant by ‘out of phase’?

Answer 13

Wave is neither in phase or anti phase.

Question 14

What is ‘anti phase’?

Answer 14

Difference of exactly 𝝅 (180 degrees) between the phase of 2 waves.

Question 15

Path Difference

Answer 15

Difference in distance covered by wave.

Question 16

When ‘n’ is an integer and in terms of 𝝺. Describe these waves.

-> (n + 0.5)
-> (n)
-> (n+3.5)
-> (n+7)
-> (n+0.85)

Answer 16

• Anti phase
• Phase
• Antiphase
• Phase
• Out of phase

Question 17

Do waves in phase have to have the same amplitude?

Answer 17

No but must cross medium at same point and have max displacement at the same time.

Question 18

Why do longitudinal waves speed up in denser materials

Answer 18

Because of closer atomic structure energy can transfer faster.

Question 19

How to light waves oscillate about the direction of energy transfer?

Answer 19

Perpendicular

Question 20

What equation should you use when looking at graphs?

Answer 20

y = mx + c

Question 21

Describe reflection

Answer 21

When a wave rebounds from hitting the boundary between 2 mediums.

Question 22

Describe Refraction

Answer 22

Change in direction due to moving to a different medium.

Question 23

Describe Diffraction

Answer 23

The spreading of waves around an obstacle/through a gap.

Question 24

Describe polarisation

Answer 24

Reducing number of planes a wave travels in to one.
- Only applicable to transverse waves

Question 25

Define intensity

Answer 25

Power transferred per unit area (usually by wave).
-> I = P/A (In EQ book)

Question 26

How to Em waves travel?

Answer 26

Vibrate in both electric & magnetic field.
- Transverse