Physics Test Revision - ChT on 27/12/26

Diffraction Definition

Where waves pass through a gap or an obstacle and spread out

Where does most diffraction occur?

Most diffraction occurs when λ is a similar length to the gap size.

If λ > gap

• Diffracted Waves are Circular

• λ MUST STAY THE SAME

If λ < gap

• Central part is a straight line

• Curves around the edges

• λ MUST STAY THE SAME

Rule when there is an obstacle, connection with λ

The greater the λ, the greater the diffraction

Refraction in water (Deep —> Shallow)

• Velocity DECREASE

• λ DECREASE

• Frequency =

• Wavefronts, bends TOWARDS normal.

Speed of ALL EM Waves

3.0 × 10⁸ m/s

Uses of radio waves

• Radio and TV transmissions

• Radio Frequency Identification (RFID)

Uses of microwaves

• Microwave ovens

• Mobile phone transmissions

Uses of Infrared

• Remote controllers

• Thermal imaging

Uses of Visible Light

• Photography

• Vision

Uses of Ultra-Violet (UV)

• Detecting fake bank notes

• Sterilising water

Uses of X-Rays

• Medical Scanning

• Security

Uses of Gamma Rays

• Sterilising Food

• Detection of Cancer

Microwaves Harms

Internal Burning

Infrared Harms

Skin Burns

Ultra-Violet Harms

Damage to surface cells

X-Rays, Gamma Rays Harms

Mutation to Cells in the body

Low-orbit Satellites

• around 200km above sea-level

• monitors the WEATHER

• shortened time delay compared to GOS

• signals much clearer

Geostationary Satellites

• around 36,000km above sea-level

• orbit is 24 hours

• used for RADIO ELECTROCOMMUNICATIONS

  • due to high orbit

Mobile phones use : __________

• Use MICROWAVES

  • Penetrate SOME walls

  • Only need a SHORT AERIAL for reception and transmission

Bluetooth uses : ____________

• Use RADIOWAVES

  • Able to PASS through walls

    • However signal WEAKENED after passing through walls

Optical Fibres use : _______ & ________

• Use INFRARED & VISIBLE LIGHT

  • For CABLE TELEVISION & HIGH SPEED BROADBAND

  • Glass is TRANSPERENT to VL & INFRARED

  • Able to carry LOTS OF DATA

Digital Signals Description

• Is only able to carry the values of 0 and 1s on the axis of signal strength

Analogue Signals Description

• Is able to carry an infinite range of values on the axis of signal strength

Soundwaves are transmitted and undergo : ________

Digital Sampling

Digital Sampling Process

Before Transformation : Analogue —> Digital

After Received : Digital —> Analogue

Benefits of Digital Sampling

• Increased RATE of data transmission

• Increased RANGE of transmission

• More DIFFICULT to corrupt