TOPIC 11: WAVES

Question 1

3 Main Types of Waves

Answer 1

Mechanical Waves
Electromagnetic Waves
Matter Waves (JC 2)

Question 2

What is the speed of a progressive wave equivalent to?

Answer 2

Speed at which energy is transferred

Question 3

[Definition] Wavelength

Answer 3

The wavelength of a wave is the minimum distance between two points with the same phase

Question 4

[Formula] Speed of Wave

Answer 4

v = fλ

Question 5

[Formula] Phase Difference

Answer 5

ΔΦ = Δt/T = Δs/λ

Question 6

[Definition] Transverse Wave

Answer 6

A transverse wave is one where the oscillations are normal to the direction of energy propagation

Question 7

[Definition] Longitudinal Wave

Answer 7

A longitudinal wave is one where the oscillations are parallel to the direction of energy propagation

Question 8

[Definition] Intensity

Answer 8

The intensity of a wave is the rate of energy flow per unit area that is perpendicular to the direction of wave propagation

Question 9

[Formula] Intensity - for 3 scenarios

Answer 9

Planar wavefronts: I = P/A
Circular wavefronts: I = P/(2πr) [I ∝ 1/r)
Spherical wavefronts: I = P/(4πr²) [I ∝ 1/r²)

Question 10

[Formula] Relating intensity and amplitude

Answer 10

I ∝ (amplitude)²

Question 11

What is a polarised wave?

Answer 11

In a polarised wave, the oscillations are along one direction only, in a single plane that is normal to the direction of energy transfer of the wave

*Only transverse wave can be polarised

Question 12

[Formula] Relating intensity and polarising angle

Answer 12

x = x₀cosθ
I = I₀cos²θ

I₁ = 1/2 I₀