IN PROGRESS 🔉 Waves & Optics

What is amplitude?

The maximum displacement from the equilibrium (centre of displacement)

What is frequency?

The number of completed cycle per unit time (Hz - the number of cycle per second)

What is the frequency related to time?

$$F=\frac{1}{T}$$

What is wavelength?

The minimum distance between two points on a wave that are in phase

What does in phase mean?

There is a whole number of wavelengths between two points

What is Speed related to waves?

The distance travelled by the wave per unit time

Equation that relates speed, frequency and wavelength?

$$C=f\lambda$$

What is the phase of wave?

The fraction of a cycle covered up to that point. (Measured in degrees/radians)

What is phase difference?

How far out of sync two point on a wave(or two points on separate waves) are in degrees/radians

How to calculate Phase Difference from displacement/distance graph?

$$Phase.Difference=\frac{d}{\lambda}\times2\pi$$

$\lambda$ = wavelength

How to calculate Phase Difference from displacement/time graph?

$$Phase.Difference=\frac{t}{T}\times2\pi$$

T = time period

What is a transverse wave?

Transverse wave: The oscillations are perpendicular to the direction of energy transfer

What are Longitudinal waves?

Longitudinal wave: The oscillations are parallel to the direction of energy transfer

What occurs in longitudinal wave?

• Compression

• Rarefraction

What are the examples of transverse waves?

• Electromagnetic Waves

• Waves on a string

What speed do EM waves travel in a vacuum?

At speed of light (C)

$$3\times10^8$$

What are examples of longitudinal waves?

Sound Waves

What does polarisation mean?

Oscillating of a particle or field that only travel in one single plane

What types of waves can be polarised and why?

Only transverse waves can be polarised as oscillations are perpendicular to energy transfer

What are different types of polarisation?

What is an example of a non polarised wave?

Unreflected Sunlight

What are application of polarisation?

• Polarised sunglasses

• Alignment of aerials for transmission and reception

How do properties of sunlight change when reflected on reflective material?

Before: Non polarised wave

After: Mostly polarised horizontally

How do vertically polarising sunglasses work to reduce glare/reflections?

1. When sun light is reflected on reflective surface (water) it becomes mostly horizontal polarised

2. The vertical polarised absorb this horizontally polarised light and only the minimal vertically polarised light is let through- reducing glare

3. When light hit other objects it remains unpolarised so only 50% of light will pass through Polaroids

How to are polarised waves used for alignment of aerials for transmission and reception?

• The receptor can be rotated vertically- if maximum signal then transmitter waves are polarised in vertical plane

• The receptor can be rotated horizontally - if maximum signal then transmitter waves are polarised in horizontal plane