Physics: Waves and the Electromagnetic Spectrum

A set of vocabulary flashcards covering wave properties, wave equations, light behaviors (reflection, refraction, diffraction), and the electromagnetic spectrum based on the lecture notes.

Wave

A phenomenon that transfers energy from one point to another without transferring matter.

Oscillations

Vibrations about a fixed point, such as water particles moving up and down or air particles moving back and forth.

Wavefront

A single line used to represent a single wave when picturing waves from above.

Amplitude ($A$)

The maximum displacement of a wave from its undisturbed position, measured in metres ($m$).

Wavelength ($\lambda$)

The distance from one point on the wave to the same point on the next wave, measured in metres ($m$).

Frequency ($f$)

The number of waves passing a point in a second, measured in hertz ($Hz$).

Crest

The highest point on a wave above its undisturbed position; also known as a peak.

Trough

The lowest point on a wave below its undisturbed position.

Wave speed ($v$)

The distance travelled by a wave each second and the speed at which energy is transferred through a medium.

Wave Equation

The relationship defined as $v = f \times \text{λ}$, where $v$ is wave speed ($m/s$), $f$ is frequency ($Hz$), and $\text{λ}$ is wavelength ($m$).

Medium

A transparent material in optics; multiple such materials are referred to as media.

Normal line

An imaginary line drawn perpendicular ($90^\text{o}$) to the boundary between two media.

Reflection

Occurs when a wave hits a boundary between two media at a plane surface and stays in the original medium instead of passing through.

Refraction

The change in speed, wavelength, and direction that occurs when a wave passes a boundary between two different transparent media.

Diffraction

The spreading out of waves when they pass through a narrow gap.

Angle of incidence ($i$)

The angle of the wave approaching the boundary, measured between the incident ray and the normal.

Angle of reflection ($r$)

The angle of the wave leaving the boundary, measured between the reflected ray and the normal.

Law of Reflection

The principle stating that the Angle of incidence ($i$) = Angle of reflection ($r$).

Virtual image

An image, such as one seen in a plane mirror, formed where virtual rays cross due to the divergence of reflected rays.

Optical density

A property of a medium that determines how much light bends; light bends towards the normal when entering a more dense medium.

Refractive index ($n$)

A unitless ratio defined as the ratio of speeds ($n = \frac{v_1}{v_2}$) or the ratio of angles ($n = \frac{\text{sin}(i)}{\text{sin}(r)}$).

Total Internal Reflection (TIR)

Occurs when all of the incident ray in an optically dense medium is reflected back at the boundary with a less dense medium.

Critical angle

The specific angle of incidence at which internal reflection occurs and beyond which total internal reflection takes place.

Optical fibres

Thin strands that utilize total internal reflection to carry light for communications or medical endoscopes.

Electromagnetic spectrum

A continuous range of radiation ordered by wavelength or frequency, consisting of radio, microwave, infrared, visible, ultraviolet, X-rays, and gamma rays.

Radio waves

Long-wavelength electromagnetic waves used for radio and television transmissions and RFID.

Microwaves

Electromagnetic waves used for satellite communications and mobile phones; can cause internal heating of body cells.

Infrared

Radiation used for television remote controllers, thermal imaging, and optical fibres; can cause skin burns.

Ultraviolet

Radiation used for security marking and sterilising water; excessive exposure can lead to skin cancer and eye conditions.

X-rays

High-frequency radiation used for medical scanning; can penetrate soft tissues but not bone.

Gamma rays

Highly ionising radiation used for sterilising medical equipment and cancer treatment.

Ionisation

The process by which high-energy radiation (UV, X-rays, gamma) harms cells and causes cancer by removing electrons from atoms.