Waves Y11

What does EM spectrum stand for?

Electromagnetic spectrum: the range of all electromagnetic waves

Order of the EM spectrum (low to high frequency)

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

How do wavelength and frequency change across the EM spectrum?

Frequency increases and wavelength decreases

Which EM waves have the longest wavelength?

Radio waves

Which EM waves have the shortest wavelength?

Gamma rays

Use of radio waves

Communication such as TV and radio

Hazard of radio waves

Little to no hazard at normal exposure

Use of microwaves

Cooking food and satellite communication

Hazard of microwaves

Internal heating of body tissue

Use of infrared

Heaters and thermal imaging

Hazard of infrared

Skin burns

Use of visible light

Seeing

Hazard of visible light

Eye damage if too bright

Use of ultraviolet (UV)

Tanning and sterilising

Hazard of ultraviolet

Skin cancer and eye damage

Use of X-rays

Medical imaging

Hazard of X-rays

Cell mutation and cancer

Use of gamma rays

Sterilising equipment and cancer treatment

Hazard of gamma rays

Severe cell damage and cancer

What is reflection?

When a wave bounces off a surface

Law of reflection

The angle of incidence equals the angle of reflection

What is the normal?

A line perpendicular to the surface

Specular reflection

Reflection from smooth surfaces forming a clear image

Diffuse reflection

Reflection from rough surfaces so no clear image is formed

What is refraction?

A change in direction of a wave when it crosses a boundary between media

Why does refraction occur?

The wave changes speed when entering a different medium

What happens to frequency during refraction?

Frequency stays the same

Light entering a denser medium

Slows down, wavelength decreases, bends towards the normal

Light leaving a denser medium

Speeds up, wavelength increases, bends away from the normal

When does light not change direction during refraction?

When it travels along the normal

What colours make up white light?

Red, green and blue

How do we see colour?

Objects reflect some colours and absorb others

What does a red object do to light?

Reflects red light and absorbs other colours

What does a colour filter do?

Transmits its own colour and absorbs others

What happens if a red filter and a blue filter overlap?

No light is transmitted