Physics: Waves, Electromagnetic Spectrum, and Radioactive Decay

Wavelength

The distance between two consecutive crests or troughs of a wave.

Frequency

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

Amplitude

The height of a wave from its rest position, showing its energy level.

Wave speed formula

v = f × λ

Electromagnetic spectrum order

Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma ray.

Radio waves

Used for broadcasting and communication.

Microwaves

Used for cooking and radar; can heat body tissue.

Infrared waves

Used for thermal imaging and remote controls; too much causes burns.

Visible light

Used for vision and photography; generally safe.

Ultraviolet radiation

Used for sterilisation and tanning; causes sunburn and skin cancer.

X-rays

Used for medical imaging; can damage cells and cause mutations.

Gamma rays

Used for cancer treatment and sterilising equipment; highly dangerous and penetrating.

Reflection

When a wave bounces off a surface, like light on a mirror.

Refraction

The bending of a wave as it passes into a different medium.

Absorption

When a material takes in the energy of a wave.

Transmission

When a wave passes through a material.

Radioactive atoms

Atoms are radioactive because their nuclei are unstable and emit radiation to become stable.

Types of nuclear radiation

Alpha, beta, and gamma.

Least penetrating radiation

Alpha particles (stopped by paper or skin).

Radiation stopped by aluminium

Beta particles.

Most penetrating radiation

Gamma rays (stopped by thick lead).

Atoms composition

Atoms are made of protons, neutrons, and electrons.

Nucleus composition

Protons and neutrons are found in the nucleus.

Isotope

Atoms with the same number of protons but different numbers of neutrons.

Radioactive decay

The process where unstable nuclei emit radiation to become stable.

Radiocarbon dating

Used for determining the age of once-living materials using carbon-14 decay.

Half-life

The time it takes for half of a radioactive sample to decay.

Half-life calculation

If a sample has a half-life of 10 years and starts with 100 g, 25 g is left after 20 years.